These patches include few backported fixes for the 4.4 stable tree. I would appreciate if you could kindly consider including them in the next release.
Ajay
---
[Changes from v1]: No changes, only answering Greg's below queries:
Why are these needed? From what I remember, the last patch here is only needed for machines that are "HUGE" and for those, you shouldn't be using 4.4.y anymore anyway, right? You just end up saving so much more speed and energy using a newer kernel, why would you want to waste it using an older one?
So I need a really good reason why to accept these :)
It's been a week, so I'm dropping this from my queue now. Please resend with this information if you still want these in the tree.
thanks, greg k-h
Indeed, the machine needs to have about 140 GB of RAM to exploit this vulnerability (CVE-2019-11487). However, Photon OS doesn't impose any limits on the amount of RAM that it supports, so we would like to safeguard the kernel against this CVE. Also, while newer versions of Photon OS are on more recent kernels, Photon OS 1.0 uses the 4.4 stable series, so it would be great to get these patches included in an upcoming 4.4 stable release.
We would also like to have the following patches that are for machines that are huge:
Patch 1: Introduced page_ref_zero_or_close_to_overflow() which helps to check for small underflows (or _very_ close to overflowing), and ignore overflows which have strayed into negative territory. And this is being used inside get_page() and get_page_foll() to reduce the possibility of overflowing.
Patch 6: Attacker could do direct IO on a page multiple times to trigger an overflowing. This patch makes get_user_pages() refuse to if there is an overflow.
Patch 8: This removes another mechanism for overflowing the page refcount inside pipe_buf_get().
---
[PATCH v2 1/8]: Backporting of upstream commit f958d7b528b1: mm: make page ref count overflow check tighter and more explicit
[PATCH v2 2/8]: Backporting of upstream commit 88b1a17dfc3e: mm: add 'try_get_page()' helper function
[PATCH v2 3/8]: Backporting of upstream commit 7aef4172c795: mm: handle PTE-mapped tail pages in gerneric fast gup implementaiton
[PATCH v2 4/8]: Backporting of upstream commit a3e328556d41: mm, gup: remove broken VM_BUG_ON_PAGE compound check for hugepages
[PATCH v2 5/8]: Backporting of upstream commit d63206ee32b6: mm, gup: ensure real head page is ref-counted when using hugepages
[PATCH v2 6/8]: Backporting of upstream commit 8fde12ca79af: mm: prevent get_user_pages() from overflowing page refcount
[PATCH v2 7/8]: Backporting of upstream commit 7bf2d1df8082: pipe: add pipe_buf_get() helper
[PATCH v2 8/8]: Backporting of upstream commit 15fab63e1e57: fs: prevent page refcount overflow in pipe_buf_get
From: Linus Torvalds torvalds@linux-foundation.org
commit f958d7b528b1b40c44cfda5eabe2d82760d868c3 upsteam.
We have a VM_BUG_ON() to check that the page reference count doesn't underflow (or get close to overflow) by checking the sign of the count.
That's all fine, but we actually want to allow people to use a "get page ref unless it's already very high" helper function, and we want that one to use the sign of the page ref (without triggering this VM_BUG_ON).
Change the VM_BUG_ON to only check for small underflows (or _very_ close to overflowing), and ignore overflows which have strayed into negative territory.
Acked-by: Matthew Wilcox willy@infradead.org Cc: Jann Horn jannh@google.com Cc: stable@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ 4.4.y backport notes: Ajay: Open-coded atomic refcount access due to missing page_ref_count() helper in 4.4.y Srivatsa: Added overflow check to get_page_foll() and related code. ] Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Ajay Kaher akaher@vmware.com --- include/linux/mm.h | 6 +++++- mm/internal.h | 5 +++-- 2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h index ed653ba..701088e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -488,6 +488,10 @@ static inline void get_huge_page_tail(struct page *page)
extern bool __get_page_tail(struct page *page);
+/* 127: arbitrary random number, small enough to assemble well */ +#define page_ref_zero_or_close_to_overflow(page) \ + ((unsigned int) atomic_read(&page->_count) + 127u <= 127u) + static inline void get_page(struct page *page) { if (unlikely(PageTail(page))) @@ -497,7 +501,7 @@ static inline void get_page(struct page *page) * Getting a normal page or the head of a compound page * requires to already have an elevated page->_count. */ - VM_BUG_ON_PAGE(atomic_read(&page->_count) <= 0, page); + VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page); atomic_inc(&page->_count); }
diff --git a/mm/internal.h b/mm/internal.h index f63f439..67015e5 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -81,7 +81,8 @@ static inline void __get_page_tail_foll(struct page *page, * speculative page access (like in * page_cache_get_speculative()) on tail pages. */ - VM_BUG_ON_PAGE(atomic_read(&compound_head(page)->_count) <= 0, page); + VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(compound_head(page)), + page); if (get_page_head) atomic_inc(&compound_head(page)->_count); get_huge_page_tail(page); @@ -106,7 +107,7 @@ static inline void get_page_foll(struct page *page) * Getting a normal page or the head of a compound page * requires to already have an elevated page->_count. */ - VM_BUG_ON_PAGE(atomic_read(&page->_count) <= 0, page); + VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page); atomic_inc(&page->_count); } }
From: Linus Torvalds torvalds@linux-foundation.org
commit 88b1a17dfc3ed7728316478fae0f5ad508f50397 upsteam.
This is the same as the traditional 'get_page()' function, but instead of unconditionally incrementing the reference count of the page, it only does so if the count was "safe". It returns whether the reference count was incremented (and is marked __must_check, since the caller obviously has to be aware of it).
Also like 'get_page()', you can't use this function unless you already had a reference to the page. The intent is that you can use this exactly like get_page(), but in situations where you want to limit the maximum reference count.
The code currently does an unconditional WARN_ON_ONCE() if we ever hit the reference count issues (either zero or negative), as a notification that the conditional non-increment actually happened.
NOTE! The count access for the "safety" check is inherently racy, but that doesn't matter since the buffer we use is basically half the range of the reference count (ie we look at the sign of the count).
Acked-by: Matthew Wilcox willy@infradead.org Cc: Jann Horn jannh@google.com Cc: stable@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ 4.4.y backport notes: Srivatsa: - Adapted try_get_page() to match the get_page() implementation in 4.4.y, except for the refcount check. - Added try_get_page_foll() which will be needed in a subsequent patch. ] Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Ajay Kaher akaher@vmware.com --- include/linux/mm.h | 12 ++++++++++++ mm/internal.h | 23 +++++++++++++++++++++++ 2 files changed, 35 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h index 701088e..52edaf1 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -505,6 +505,18 @@ static inline void get_page(struct page *page) atomic_inc(&page->_count); }
+static inline __must_check bool try_get_page(struct page *page) +{ + if (unlikely(PageTail(page))) + if (likely(__get_page_tail(page))) + return true; + + if (WARN_ON_ONCE(atomic_read(&page->_count) <= 0)) + return false; + atomic_inc(&page->_count); + return true; +} + static inline struct page *virt_to_head_page(const void *x) { struct page *page = virt_to_page(x); diff --git a/mm/internal.h b/mm/internal.h index 67015e5..d83afc9 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -112,6 +112,29 @@ static inline void get_page_foll(struct page *page) } }
+static inline __must_check bool try_get_page_foll(struct page *page) +{ + if (unlikely(PageTail(page))) { + if (WARN_ON_ONCE(atomic_read(&compound_head(page)->_count) <= 0)) + return false; + /* + * This is safe only because + * __split_huge_page_refcount() can't run under + * get_page_foll() because we hold the proper PT lock. + */ + __get_page_tail_foll(page, true); + } else { + /* + * Getting a normal page or the head of a compound page + * requires to already have an elevated page->_count. + */ + if (WARN_ON_ONCE(atomic_read(&page->_count) <= 0)) + return false; + atomic_inc(&page->_count); + } + return true; +} + extern unsigned long highest_memmap_pfn;
/*
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
commit 7aef4172c7957d7e65fc172be4c99becaef855d4 upstream.
With new refcounting we are going to see THP tail pages mapped with PTE. Generic fast GUP rely on page_cache_get_speculative() to obtain reference on page. page_cache_get_speculative() always fails on tail pages, because ->_count on tail pages is always zero.
Let's handle tail pages in gup_pte_range().
New split_huge_page() will rely on migration entries to freeze page's counts. Recheck PTE value after page_cache_get_speculative() on head page should be enough to serialize against split.
Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Tested-by: Sasha Levin sasha.levin@oracle.com Tested-by: Aneesh Kumar K.V aneesh.kumar@linux.vnet.ibm.com Acked-by: Jerome Marchand jmarchan@redhat.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Andrea Arcangeli aarcange@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Dave Hansen dave.hansen@intel.com Cc: Mel Gorman mgorman@suse.de Cc: Rik van Riel riel@redhat.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Steve Capper steve.capper@linaro.org Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@suse.cz Cc: Christoph Lameter cl@linux.com Cc: David Rientjes rientjes@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ajay Kaher akaher@vmware.com --- mm/gup.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 2cd3b31..45c544b 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1070,7 +1070,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, * for an example see gup_get_pte in arch/x86/mm/gup.c */ pte_t pte = READ_ONCE(*ptep); - struct page *page; + struct page *head, *page;
/* * Similar to the PMD case below, NUMA hinting must take slow @@ -1082,15 +1082,17 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); + head = compound_head(page);
- if (!page_cache_get_speculative(page)) + if (!page_cache_get_speculative(head)) goto pte_unmap;
if (unlikely(pte_val(pte) != pte_val(*ptep))) { - put_page(page); + put_page(head); goto pte_unmap; }
+ VM_BUG_ON_PAGE(compound_head(page) != head, page); pages[*nr] = page; (*nr)++;
From: Will Deacon will.deacon@arm.com
commit a3e328556d41bb61c55f9dfcc62d6a826ea97b85 upstream.
When operating on hugepages with DEBUG_VM enabled, the GUP code checks the compound head for each tail page prior to calling page_cache_add_speculative. This is broken, because on the fast-GUP path (where we don't hold any page table locks) we can be racing with a concurrent invocation of split_huge_page_to_list.
split_huge_page_to_list deals with this race by using page_ref_freeze to freeze the page and force concurrent GUPs to fail whilst the component pages are modified. This modification includes clearing the compound_head field for the tail pages, so checking this prior to a successful call to page_cache_add_speculative can lead to false positives: In fact, page_cache_add_speculative *already* has this check once the page refcount has been successfully updated, so we can simply remove the broken calls to VM_BUG_ON_PAGE.
Link: http://lkml.kernel.org/r/20170522133604.11392-2-punit.agrawal@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Punit Agrawal punit.agrawal@arm.com Acked-by: Steve Capper steve.capper@arm.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.vnet.ibm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Mark Rutland mark.rutland@arm.com Cc: Hillf Danton hillf.zj@alibaba-inc.com Cc: Michal Hocko mhocko@suse.com Cc: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Ajay Kaher akaher@vmware.com --- mm/gup.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 45c544b..6e7cfaa 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1136,7 +1136,6 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); tail = page; do { - VM_BUG_ON_PAGE(compound_head(page) != head, page); pages[*nr] = page; (*nr)++; page++; @@ -1183,7 +1182,6 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); tail = page; do { - VM_BUG_ON_PAGE(compound_head(page) != head, page); pages[*nr] = page; (*nr)++; page++; @@ -1226,7 +1224,6 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); tail = page; do { - VM_BUG_ON_PAGE(compound_head(page) != head, page); pages[*nr] = page; (*nr)++; page++;
From: Punit Agrawal punit.agrawal@arm.com
commit d63206ee32b6e64b0e12d46e5d6004afd9913713 upstream.
When speculatively taking references to a hugepage using page_cache_add_speculative() in gup_huge_pmd(), it is assumed that the page returned by pmd_page() is the head page. Although normally true, this assumption doesn't hold when the hugepage comprises of successive page table entries such as when using contiguous bit on arm64 at PTE or PMD levels.
This can be addressed by ensuring that the page passed to page_cache_add_speculative() is the real head or by de-referencing the head page within the function.
We take the first approach to keep the usage pattern aligned with page_cache_get_speculative() where users already pass the appropriate page, i.e., the de-referenced head.
Apply the same logic to fix gup_huge_[pud|pgd]() as well.
[punit.agrawal@arm.com: fix arm64 ltp failure] Link: http://lkml.kernel.org/r/20170619170145.25577-5-punit.agrawal@arm.com Link: http://lkml.kernel.org/r/20170522133604.11392-3-punit.agrawal@arm.com Signed-off-by: Punit Agrawal punit.agrawal@arm.com Acked-by: Steve Capper steve.capper@arm.com Cc: Michal Hocko mhocko@suse.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.vnet.ibm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Mark Rutland mark.rutland@arm.com Cc: Hillf Danton hillf.zj@alibaba-inc.com Cc: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ajay Kaher akaher@vmware.com Reviewed-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu --- mm/gup.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 6e7cfaa..fae4d1e 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1132,8 +1132,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, return 0;
refs = 0; - head = pmd_page(orig); - page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); tail = page; do { pages[*nr] = page; @@ -1142,6 +1141,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
+ head = compound_head(pmd_page(orig)); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1178,8 +1178,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, return 0;
refs = 0; - head = pud_page(orig); - page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); tail = page; do { pages[*nr] = page; @@ -1188,6 +1187,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
+ head = compound_head(pud_page(orig)); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1220,8 +1220,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, return 0;
refs = 0; - head = pgd_page(orig); - page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); tail = page; do { pages[*nr] = page; @@ -1230,6 +1229,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
+ head = compound_head(pgd_page(orig)); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0;
From: Linus Torvalds torvalds@linux-foundation.org
commit 8fde12ca79aff9b5ba951fce1a2641901b8d8e64 upstream.
If the page refcount wraps around past zero, it will be freed while there are still four billion references to it. One of the possible avenues for an attacker to try to make this happen is by doing direct IO on a page multiple times. This patch makes get_user_pages() refuse to take a new page reference if there are already more than two billion references to the page.
Reported-by: Jann Horn jannh@google.com Acked-by: Matthew Wilcox willy@infradead.org Cc: stable@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ 4.4.y backport notes: Ajay: Added local variable 'err' with-in follow_hugetlb_page() from 2be7cfed995e, to resolve compilation error Srivatsa: Replaced call to get_page_foll() with try_get_page_foll() ] Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Ajay Kaher akaher@vmware.com --- mm/gup.c | 43 ++++++++++++++++++++++++++++++++----------- mm/hugetlb.c | 16 +++++++++++++++- 2 files changed, 47 insertions(+), 12 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index fae4d1e..171b460 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -126,8 +126,12 @@ retry: } }
- if (flags & FOLL_GET) - get_page_foll(page); + if (flags & FOLL_GET) { + if (unlikely(!try_get_page_foll(page))) { + page = ERR_PTR(-ENOMEM); + goto out; + } + } if (flags & FOLL_TOUCH) { if ((flags & FOLL_WRITE) && !pte_dirty(pte) && !PageDirty(page)) @@ -289,7 +293,10 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, goto unmap; *page = pte_page(*pte); } - get_page(*page); + if (unlikely(!try_get_page(*page))) { + ret = -ENOMEM; + goto unmap; + } out: ret = 0; unmap: @@ -1053,6 +1060,20 @@ struct page *get_dump_page(unsigned long addr) */ #ifdef CONFIG_HAVE_GENERIC_RCU_GUP
+/* + * Return the compund head page with ref appropriately incremented, + * or NULL if that failed. + */ +static inline struct page *try_get_compound_head(struct page *page, int refs) +{ + struct page *head = compound_head(page); + if (WARN_ON_ONCE(atomic_read(&head->_count) < 0)) + return NULL; + if (unlikely(!page_cache_add_speculative(head, refs))) + return NULL; + return head; +} + #ifdef __HAVE_ARCH_PTE_SPECIAL static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) @@ -1082,9 +1103,9 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - head = compound_head(page);
- if (!page_cache_get_speculative(head)) + head = try_get_compound_head(page, 1); + if (!head) goto pte_unmap;
if (unlikely(pte_val(pte) != pte_val(*ptep))) { @@ -1141,8 +1162,8 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
- head = compound_head(pmd_page(orig)); - if (!page_cache_add_speculative(head, refs)) { + head = try_get_compound_head(pmd_page(orig), refs); + if (!head) { *nr -= refs; return 0; } @@ -1187,8 +1208,8 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
- head = compound_head(pud_page(orig)); - if (!page_cache_add_speculative(head, refs)) { + head = try_get_compound_head(pud_page(orig), refs); + if (!head) { *nr -= refs; return 0; } @@ -1229,8 +1250,8 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
- head = compound_head(pgd_page(orig)); - if (!page_cache_add_speculative(head, refs)) { + head = try_get_compound_head(pgd_page(orig), refs); + if (!head) { *nr -= refs; return 0; } diff --git a/mm/hugetlb.c b/mm/hugetlb.c index fd932e7..3a1501e 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3886,6 +3886,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long vaddr = *position; unsigned long remainder = *nr_pages; struct hstate *h = hstate_vma(vma); + int err = -EFAULT;
while (vaddr < vma->vm_end && remainder) { pte_t *pte; @@ -3957,6 +3958,19 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT; page = pte_page(huge_ptep_get(pte)); + + /* + * Instead of doing 'try_get_page_foll()' below in the same_page + * loop, just check the count once here. + */ + if (unlikely(page_count(page) <= 0)) { + if (pages) { + spin_unlock(ptl); + remainder = 0; + err = -ENOMEM; + break; + } + } same_page: if (pages) { pages[i] = mem_map_offset(page, pfn_offset); @@ -3983,7 +3997,7 @@ same_page: *nr_pages = remainder; *position = vaddr;
- return i ? i : -EFAULT; + return i ? i : err; }
unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
On 10/9/19 2:44 AM, Ajay Kaher wrote:
From: Linus Torvalds torvalds@linux-foundation.org
commit 8fde12ca79aff9b5ba951fce1a2641901b8d8e64 upstream.
If the page refcount wraps around past zero, it will be freed while there are still four billion references to it. One of the possible avenues for an attacker to try to make this happen is by doing direct IO on a page multiple times. This patch makes get_user_pages() refuse to take a new page reference if there are already more than two billion references to the page.
Reported-by: Jann Horn jannh@google.com Acked-by: Matthew Wilcox willy@infradead.org Cc: stable@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ 4.4.y backport notes: Ajay: Added local variable 'err' with-in follow_hugetlb_page() from 2be7cfed995e, to resolve compilation error Srivatsa: Replaced call to get_page_foll() with try_get_page_foll() ] Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Ajay Kaher akaher@vmware.com
mm/gup.c | 43 ++++++++++++++++++++++++++++++++----------- mm/hugetlb.c | 16 +++++++++++++++- 2 files changed, 47 insertions(+), 12 deletions(-)
This seems to have the same issue as the 4.9 stable version [1], in not touching the arch-specific gup.c variants.
[1] https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@suse.cz/
diff --git a/mm/gup.c b/mm/gup.c index fae4d1e..171b460 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -126,8 +126,12 @@ retry: } }
- if (flags & FOLL_GET)
get_page_foll(page);
- if (flags & FOLL_GET) {
if (unlikely(!try_get_page_foll(page))) {page = ERR_PTR(-ENOMEM);goto out;}- } if (flags & FOLL_TOUCH) { if ((flags & FOLL_WRITE) && !pte_dirty(pte) && !PageDirty(page))
@@ -289,7 +293,10 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, goto unmap; *page = pte_page(*pte); }
- get_page(*page);
- if (unlikely(!try_get_page(*page))) {
ret = -ENOMEM;goto unmap;- }
out: ret = 0; unmap: @@ -1053,6 +1060,20 @@ struct page *get_dump_page(unsigned long addr) */ #ifdef CONFIG_HAVE_GENERIC_RCU_GUP +/*
- Return the compund head page with ref appropriately incremented,
- or NULL if that failed.
- */
+static inline struct page *try_get_compound_head(struct page *page, int refs) +{
- struct page *head = compound_head(page);
- if (WARN_ON_ONCE(atomic_read(&head->_count) < 0))
return NULL;- if (unlikely(!page_cache_add_speculative(head, refs)))
return NULL;- return head;
+}
#ifdef __HAVE_ARCH_PTE_SPECIAL static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) @@ -1082,9 +1103,9 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte);
head = compound_head(page);
if (!page_cache_get_speculative(head))
head = try_get_compound_head(page, 1);if (!head) goto pte_unmap;if (unlikely(pte_val(pte) != pte_val(*ptep))) { @@ -1141,8 +1162,8 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
- head = compound_head(pmd_page(orig));
- if (!page_cache_add_speculative(head, refs)) {
- head = try_get_compound_head(pmd_page(orig), refs);
- if (!head) { *nr -= refs; return 0; }
@@ -1187,8 +1208,8 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
- head = compound_head(pud_page(orig));
- if (!page_cache_add_speculative(head, refs)) {
- head = try_get_compound_head(pud_page(orig), refs);
- if (!head) { *nr -= refs; return 0; }
@@ -1229,8 +1250,8 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end);
- head = compound_head(pgd_page(orig));
- if (!page_cache_add_speculative(head, refs)) {
- head = try_get_compound_head(pgd_page(orig), refs);
- if (!head) { *nr -= refs; return 0; }
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index fd932e7..3a1501e 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3886,6 +3886,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long vaddr = *position; unsigned long remainder = *nr_pages; struct hstate *h = hstate_vma(vma);
- int err = -EFAULT;
while (vaddr < vma->vm_end && remainder) { pte_t *pte; @@ -3957,6 +3958,19 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT; page = pte_page(huge_ptep_get(pte));
/** Instead of doing 'try_get_page_foll()' below in the same_page* loop, just check the count once here.*/if (unlikely(page_count(page) <= 0)) {if (pages) {spin_unlock(ptl);remainder = 0;err = -ENOMEM;break;}}same_page: if (pages) { pages[i] = mem_map_offset(page, pfn_offset); @@ -3983,7 +3997,7 @@ same_page: *nr_pages = remainder; *position = vaddr;
- return i ? i : -EFAULT;
- return i ? i : err;
} unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
On 09/10/19, 6:43 PM, "Vlastimil Babka" vbabka@suse.cz wrote:
Reported-by: Jann Horn jannh@google.com Acked-by: Matthew Wilcox willy@infradead.org Cc: stable@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ 4.4.y backport notes: Ajay: Added local variable 'err' with-in follow_hugetlb_page() from 2be7cfed995e, to resolve compilation error Srivatsa: Replaced call to get_page_foll() with try_get_page_foll() ] Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Ajay Kaher akaher@vmware.com
mm/gup.c | 43 ++++++++++++++++++++++++++++++++----------- mm/hugetlb.c | 16 +++++++++++++++- 2 files changed, 47 insertions(+), 12 deletions(-)
This seems to have the same issue as the 4.9 stable version [1], in not touching the arch-specific gup.c variants. [1] https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@suse.cz/
Thanks Vlastimil for highlighting this here.
Yes, arch-specific gup.c variants also need to handle not only for 4.4.y, however it should be handled till 4.19.y. I believe it's better to start from 4.19.y and then backport those changes till 4.4.y.
Affected areas of gup.c (where page->count have been used) are: #1: get_page() used in these files and this is safe as it's defined in mm.h (here it's already taken care of) #2: get_head_page_multiple() has following: VM_BUG_ON_PAGE(page_count(page) == 0, page); Need to change this to: VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page); #3: Some of the files have used page_cache_get_speculative(), page_cache_add_speculative() with combination of compound_head(), this scenario needs to be handled as it was handled here: https://lore.kernel.org/stable/1570581863-12090-7-git-send-email-akaher@vmwa...
Please share with me any suggestions or patches if you have already worked on this.
Could we handle arch-specific gup.c in different patch sets and let these patches to merge to 4.4.y?
- Ajay
On 17/10/19, 9:58 PM, "Ajay Kaher" akaher@vmware.com wrote:
This seems to have the same issue as the 4.9 stable version [1], in not touching the arch-specific gup.c variants. [1] https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@suse.cz/
Thanks Vlastimil for highlighting this here.
Yes, arch-specific gup.c variants also need to handle not only for 4.4.y, however it should be handled till 4.19.y. I believe it's better to start from 4.19.y and then backport those changes till 4.4.y. Affected areas of gup.c (where page->count have been used) are: #1: get_page() used in these files and this is safe as it's defined in mm.h (here it's already taken care of) #2: get_head_page_multiple() has following: VM_BUG_ON_PAGE(page_count(page) == 0, page); Need to change this to: VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page); #3: Some of the files have used page_cache_get_speculative(), page_cache_add_speculative() with combination of compound_head(), this scenario needs to be handled as it was handled here: https://lore.kernel.org/stable/1570581863-12090-7-git-send-email-akaher@vmwa... Please share with me any suggestions or patches if you have already worked on this. Could we handle arch-specific gup.c in different patch sets and let these patches to merge to 4.4.y?
Vlastimil, please suggest if it's fine to merge these patches to 4.4.y and handle arch-specific gup.c in different patch sets starts from 4.19.y, then backport all the way to 4.4.y.
Greg, any suggestion from your side.
- Ajay
On 10/25/19 8:18 AM, Ajay Kaher wrote:
On 17/10/19, 9:58 PM, "Ajay Kaher" akaher@vmware.com wrote:
This seems to have the same issue as the 4.9 stable version [1], in not touching the arch-specific gup.c variants. [1] https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@suse.cz/
Thanks Vlastimil for highlighting this here.
Yes, arch-specific gup.c variants also need to handle not only for 4.4.y, however it should be handled till 4.19.y. I believe it's better to start from 4.19.y and then backport those changes till 4.4.y. Affected areas of gup.c (where page->count have been used) are: #1: get_page() used in these files and this is safe as it's defined in mm.h (here it's already taken care of) #2: get_head_page_multiple() has following: VM_BUG_ON_PAGE(page_count(page) == 0, page); Need to change this to: VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page); #3: Some of the files have used page_cache_get_speculative(), page_cache_add_speculative() with combination of compound_head(), this scenario needs to be handled as it was handled here: https://lore.kernel.org/stable/1570581863-12090-7-git-send-email-akaher@vmwa... Please share with me any suggestions or patches if you have already worked on this. Could we handle arch-specific gup.c in different patch sets and let these patches to merge to 4.4.y?
Vlastimil, please suggest if it's fine to merge these patches to 4.4.y
I'm not sure if it makes much sense to merge them without the arch-specific gup support, when we're aware that it's missing.
and handle arch-specific gup.c in different patch sets starts from 4.19.y,
Actually arch-specific gup.c were removed in 4.13, so it's enough to start from 4.9.y, which I'm going to finally look into.
then backport all the way to 4.4.y.
Greg, any suggestion from your side.
- Ajay
On 06/11/19, 2:25 PM, "Vlastimil Babka" vbabka@suse.cz wrote:
On 10/25/19 8:18 AM, Ajay Kaher wrote:
On 17/10/19, 9:58 PM, "Ajay Kaher" akaher@vmware.com wrote:
Could we handle arch-specific gup.c in different patch sets and let these patches to merge to 4.4.y?
Vlastimil, please suggest if it's fine to merge these patches to 4.4.y
I'm not sure if it makes much sense to merge them without the arch-specific gup support, when we're aware that it's missing.
and handle arch-specific gup.c in different patch sets starts from 4.19.y,
Actually arch-specific gup.c were removed in 4.13, so it's enough to start from 4.9.y, which I'm going to finally look into.
Yes x86 gup.c is removed. s390 gup.c is present till 4.19, so if you are making changes in this file for 4.4.y and 4.9.y, then same should be done for 4.14.y and v4.19.y.
- Ajay
On Mon, Nov 11, 2019 at 05:00:29AM +0000, Ajay Kaher wrote:
On 06/11/19, 2:25 PM, "Vlastimil Babka" vbabka@suse.cz wrote:
On 10/25/19 8:18 AM, Ajay Kaher wrote:
On 17/10/19, 9:58 PM, "Ajay Kaher" akaher@vmware.com wrote:
Could we handle arch-specific gup.c in different patch sets and let these patches to merge to 4.4.y?
Vlastimil, please suggest if it's fine to merge these patches to 4.4.y
I'm not sure if it makes much sense to merge them without the arch-specific gup support, when we're aware that it's missing.
and handle arch-specific gup.c in different patch sets starts from 4.19.y,
Actually arch-specific gup.c were removed in 4.13, so it's enough to start from 4.9.y, which I'm going to finally look into.
Yes x86 gup.c is removed. s390 gup.c is present till 4.19, so if you are making changes in this file for 4.4.y and 4.9.y, then same should be done for 4.14.y and v4.19.y.
Ok, I have no idea what to do here. I have two different series from both of you, yet they are different.
Can you both come up with a series you agree on, and send it to me, with both of your acks so that I know this is what should be applied? I've deleted both of your current series from my todo mbox.
thanks,
greg k-h
On 11/21/19 9:38 PM, gregkh@linuxfoundation.org wrote:
On Mon, Nov 11, 2019 at 05:00:29AM +0000, Ajay Kaher wrote:
On 06/11/19, 2:25 PM, "Vlastimil Babka" vbabka@suse.cz wrote:
On 10/25/19 8:18 AM, Ajay Kaher wrote:
On 17/10/19, 9:58 PM, "Ajay Kaher" akaher@vmware.com wrote:
Could we handle arch-specific gup.c in different patch sets and let these patches to merge to 4.4.y?
Vlastimil, please suggest if it's fine to merge these patches to 4.4.y
I'm not sure if it makes much sense to merge them without the arch-specific gup support, when we're aware that it's missing.
and handle arch-specific gup.c in different patch sets starts from 4.19.y,
Actually arch-specific gup.c were removed in 4.13, so it's enough to start from 4.9.y, which I'm going to finally look into.
Yes x86 gup.c is removed. s390 gup.c is present till 4.19, so if you are making changes in this file for 4.4.y and 4.9.y, then same should be done for 4.14.y and v4.19.y.
Ok, I have no idea what to do here. I have two different series from both of you, yet they are different.
Can you both come up with a series you agree on, and send it to me, with both of your acks so that I know this is what should be applied? I've deleted both of your current series from my todo mbox.
I started by fixing up [1] 4.9, 4.14 and 4.19 which already got the backport, but without arch-specific gup.c variants. I'll wait for Ajay's feedback for the 4.4 series.
[1] https://lore.kernel.org/linux-mm/20191129090351.3507-1-vbabka@suse.cz/
thanks,
greg k-h
From: Miklos Szeredi mszeredi@redhat.com
commit 7bf2d1df80822ec056363627e2014990f068f7aa upstream.
Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Ajay Kaher akaher@vmware.com Reviewed-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu --- fs/fuse/dev.c | 2 +- fs/splice.c | 4 ++-- include/linux/pipe_fs_i.h | 11 +++++++++++ 3 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index f5d2d23..36a5df9 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -2052,7 +2052,7 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe, pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1); pipe->nrbufs--; } else { - ibuf->ops->get(pipe, ibuf); + pipe_buf_get(pipe, ibuf); *obuf = *ibuf; obuf->flags &= ~PIPE_BUF_FLAG_GIFT; obuf->len = rem; diff --git a/fs/splice.c b/fs/splice.c index 8398974..fde1263 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1876,7 +1876,7 @@ retry: * Get a reference to this pipe buffer, * so we can copy the contents over. */ - ibuf->ops->get(ipipe, ibuf); + pipe_buf_get(ipipe, ibuf); *obuf = *ibuf;
/* @@ -1948,7 +1948,7 @@ static int link_pipe(struct pipe_inode_info *ipipe, * Get a reference to this pipe buffer, * so we can copy the contents over. */ - ibuf->ops->get(ipipe, ibuf); + pipe_buf_get(ipipe, ibuf);
obuf = opipe->bufs + nbuf; *obuf = *ibuf; diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 24f5470..10876f3 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -115,6 +115,17 @@ struct pipe_buf_operations { void (*get)(struct pipe_inode_info *, struct pipe_buffer *); };
+/** + * pipe_buf_get - get a reference to a pipe_buffer + * @pipe: the pipe that the buffer belongs to + * @buf: the buffer to get a reference to + */ +static inline void pipe_buf_get(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + buf->ops->get(pipe, buf); +} + /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ #define PIPE_SIZE PAGE_SIZE
From: Matthew Wilcox willy@infradead.org
commit 15fab63e1e57be9fdb5eec1bbc5916e9825e9acb upstream.
Change pipe_buf_get() to return a bool indicating whether it succeeded in raising the refcount of the page (if the thing in the pipe is a page). This removes another mechanism for overflowing the page refcount. All callers converted to handle a failure.
Reported-by: Jann Horn jannh@google.com Signed-off-by: Matthew Wilcox willy@infradead.org Cc: stable@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ 4.4.y backport notes: Regarding the change in generic_pipe_buf_get(), note that page_cache_get() is the same as get_page(). See mainline commit 09cbfeaf1a5a6 "mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros" for context. ] Signed-off-by: Ajay Kaher akaher@vmware.com Reviewed-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu --- fs/fuse/dev.c | 12 ++++++------ fs/pipe.c | 4 ++-- fs/splice.c | 12 ++++++++++-- include/linux/pipe_fs_i.h | 10 ++++++---- kernel/trace/trace.c | 6 +++++- 5 files changed, 29 insertions(+), 15 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 36a5df9..16891f5 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -2031,10 +2031,8 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe, rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
ret = -EINVAL; - if (rem < len) { - pipe_unlock(pipe); - goto out; - } + if (rem < len) + goto out_free;
rem = len; while (rem) { @@ -2052,7 +2050,9 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe, pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1); pipe->nrbufs--; } else { - pipe_buf_get(pipe, ibuf); + if (!pipe_buf_get(pipe, ibuf)) + goto out_free; + *obuf = *ibuf; obuf->flags &= ~PIPE_BUF_FLAG_GIFT; obuf->len = rem; @@ -2075,13 +2075,13 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe, ret = fuse_dev_do_write(fud, &cs, len);
pipe_lock(pipe); +out_free: for (idx = 0; idx < nbuf; idx++) { struct pipe_buffer *buf = &bufs[idx]; buf->ops->release(pipe, buf); } pipe_unlock(pipe);
-out: kfree(bufs); return ret; } diff --git a/fs/pipe.c b/fs/pipe.c index 1e7263b..6534470 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -178,9 +178,9 @@ EXPORT_SYMBOL(generic_pipe_buf_steal); * in the tee() system call, when we duplicate the buffers in one * pipe into another. */ -void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) +bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { - page_cache_get(buf->page); + return try_get_page(buf->page); } EXPORT_SYMBOL(generic_pipe_buf_get);
diff --git a/fs/splice.c b/fs/splice.c index fde1263..57ccc58 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1876,7 +1876,11 @@ retry: * Get a reference to this pipe buffer, * so we can copy the contents over. */ - pipe_buf_get(ipipe, ibuf); + if (!pipe_buf_get(ipipe, ibuf)) { + if (ret == 0) + ret = -EFAULT; + break; + } *obuf = *ibuf;
/* @@ -1948,7 +1952,11 @@ static int link_pipe(struct pipe_inode_info *ipipe, * Get a reference to this pipe buffer, * so we can copy the contents over. */ - pipe_buf_get(ipipe, ibuf); + if (!pipe_buf_get(ipipe, ibuf)) { + if (ret == 0) + ret = -EFAULT; + break; + }
obuf = opipe->bufs + nbuf; *obuf = *ibuf; diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 10876f3..0b28b65 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -112,18 +112,20 @@ struct pipe_buf_operations { /* * Get a reference to the pipe buffer. */ - void (*get)(struct pipe_inode_info *, struct pipe_buffer *); + bool (*get)(struct pipe_inode_info *, struct pipe_buffer *); };
/** * pipe_buf_get - get a reference to a pipe_buffer * @pipe: the pipe that the buffer belongs to * @buf: the buffer to get a reference to + * + * Return: %true if the reference was successfully obtained. */ -static inline void pipe_buf_get(struct pipe_inode_info *pipe, +static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { - buf->ops->get(pipe, buf); + return buf->ops->get(pipe, buf); }
/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual @@ -148,7 +150,7 @@ struct pipe_inode_info *alloc_pipe_info(void); void free_pipe_info(struct pipe_inode_info *);
/* Generic pipe buffer ops functions */ -void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); +bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *); int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *); void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ae00e68..7fe8d04 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5731,12 +5731,16 @@ static void buffer_pipe_buf_release(struct pipe_inode_info *pipe, buf->private = 0; }
-static void buffer_pipe_buf_get(struct pipe_inode_info *pipe, +static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct buffer_ref *ref = (struct buffer_ref *)buf->private;
+ if (ref->ref > INT_MAX/2) + return false; + ref->ref++; + return true; }
/* Pipe buffer operations for a buffer. */
linux-stable-mirror@lists.linaro.org
-
Ajay Kaher -
gregkh＠linuxfoundation.org -
Vlastimil Babka