The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 6f86d0534fddfbd08687fa0f01479d4226bc3c3d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112020-buddy-bobbed-3c5d@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6f86d0534fddfbd08687fa0f01479d4226bc3c3d Mon Sep 17 00:00:00 2001
From: Lance Yang <lance.yang(a)linux.dev>
Date: Fri, 31 Oct 2025 20:09:55 +0800
Subject: [PATCH] mm/secretmem: fix use-after-free race in fault handler
When a page fault occurs in a secret memory file created with
`memfd_secret(2)`, the kernel will allocate a new folio for it, mark the
underlying page as not-present in the direct map, and add it to the file
mapping.
If two tasks cause a fault in the same page concurrently, both could end
up allocating a folio and removing the page from the direct map, but only
one would succeed in adding the folio to the file mapping. The task that
failed undoes the effects of its attempt by (a) freeing the folio again
and (b) putting the page back into the direct map. However, by doing
these two operations in this order, the page becomes available to the
allocator again before it is placed back in the direct mapping.
If another task attempts to allocate the page between (a) and (b), and the
kernel tries to access it via the direct map, it would result in a
supervisor not-present page fault.
Fix the ordering to restore the direct map before the folio is freed.
Link: https://lkml.kernel.org/r/20251031120955.92116-1-lance.yang@linux.dev
Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Signed-off-by: Lance Yang <lance.yang(a)linux.dev>
Reported-by: Google Big Sleep <big-sleep-vuln-reports(a)google.com>
Closes: https://lore.kernel.org/linux-mm/CAEXGt5QeDpiHTu3K9tvjUTPqo+d-=wuCNYPa+6sWK…
Acked-by: David Hildenbrand <david(a)redhat.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt(a)kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 60137305bc20..b59350daffe3 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -82,13 +82,13 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
__folio_mark_uptodate(folio);
err = filemap_add_folio(mapping, folio, offset, gfp);
if (unlikely(err)) {
- folio_put(folio);
/*
* If a split of large page was required, it
* already happened when we marked the page invalid
* which guarantees that this call won't fail
*/
set_direct_map_default_noflush(folio_page(folio, 0));
+ folio_put(folio);
if (err == -EEXIST)
goto retry;
The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 6f86d0534fddfbd08687fa0f01479d4226bc3c3d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112021-swept-idealness-9ecb@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6f86d0534fddfbd08687fa0f01479d4226bc3c3d Mon Sep 17 00:00:00 2001
From: Lance Yang <lance.yang(a)linux.dev>
Date: Fri, 31 Oct 2025 20:09:55 +0800
Subject: [PATCH] mm/secretmem: fix use-after-free race in fault handler
When a page fault occurs in a secret memory file created with
`memfd_secret(2)`, the kernel will allocate a new folio for it, mark the
underlying page as not-present in the direct map, and add it to the file
mapping.
If two tasks cause a fault in the same page concurrently, both could end
up allocating a folio and removing the page from the direct map, but only
one would succeed in adding the folio to the file mapping. The task that
failed undoes the effects of its attempt by (a) freeing the folio again
and (b) putting the page back into the direct map. However, by doing
these two operations in this order, the page becomes available to the
allocator again before it is placed back in the direct mapping.
If another task attempts to allocate the page between (a) and (b), and the
kernel tries to access it via the direct map, it would result in a
supervisor not-present page fault.
Fix the ordering to restore the direct map before the folio is freed.
Link: https://lkml.kernel.org/r/20251031120955.92116-1-lance.yang@linux.dev
Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Signed-off-by: Lance Yang <lance.yang(a)linux.dev>
Reported-by: Google Big Sleep <big-sleep-vuln-reports(a)google.com>
Closes: https://lore.kernel.org/linux-mm/CAEXGt5QeDpiHTu3K9tvjUTPqo+d-=wuCNYPa+6sWK…
Acked-by: David Hildenbrand <david(a)redhat.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt(a)kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 60137305bc20..b59350daffe3 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -82,13 +82,13 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
__folio_mark_uptodate(folio);
err = filemap_add_folio(mapping, folio, offset, gfp);
if (unlikely(err)) {
- folio_put(folio);
/*
* If a split of large page was required, it
* already happened when we marked the page invalid
* which guarantees that this call won't fail
*/
set_direct_map_default_noflush(folio_page(folio, 0));
+ folio_put(folio);
if (err == -EEXIST)
goto retry;
The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 6f86d0534fddfbd08687fa0f01479d4226bc3c3d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112022-curtly-unexpired-adae@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6f86d0534fddfbd08687fa0f01479d4226bc3c3d Mon Sep 17 00:00:00 2001
From: Lance Yang <lance.yang(a)linux.dev>
Date: Fri, 31 Oct 2025 20:09:55 +0800
Subject: [PATCH] mm/secretmem: fix use-after-free race in fault handler
When a page fault occurs in a secret memory file created with
`memfd_secret(2)`, the kernel will allocate a new folio for it, mark the
underlying page as not-present in the direct map, and add it to the file
mapping.
If two tasks cause a fault in the same page concurrently, both could end
up allocating a folio and removing the page from the direct map, but only
one would succeed in adding the folio to the file mapping. The task that
failed undoes the effects of its attempt by (a) freeing the folio again
and (b) putting the page back into the direct map. However, by doing
these two operations in this order, the page becomes available to the
allocator again before it is placed back in the direct mapping.
If another task attempts to allocate the page between (a) and (b), and the
kernel tries to access it via the direct map, it would result in a
supervisor not-present page fault.
Fix the ordering to restore the direct map before the folio is freed.
Link: https://lkml.kernel.org/r/20251031120955.92116-1-lance.yang@linux.dev
Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Signed-off-by: Lance Yang <lance.yang(a)linux.dev>
Reported-by: Google Big Sleep <big-sleep-vuln-reports(a)google.com>
Closes: https://lore.kernel.org/linux-mm/CAEXGt5QeDpiHTu3K9tvjUTPqo+d-=wuCNYPa+6sWK…
Acked-by: David Hildenbrand <david(a)redhat.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt(a)kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 60137305bc20..b59350daffe3 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -82,13 +82,13 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
__folio_mark_uptodate(folio);
err = filemap_add_folio(mapping, folio, offset, gfp);
if (unlikely(err)) {
- folio_put(folio);
/*
* If a split of large page was required, it
* already happened when we marked the page invalid
* which guarantees that this call won't fail
*/
set_direct_map_default_noflush(folio_page(folio, 0));
+ folio_put(folio);
if (err == -EEXIST)
goto retry;
The patch below does not apply to the 6.17-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.17.y
git checkout FETCH_HEAD
git cherry-pick -x 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112027-ranch-retool-efaa@gregkh' --subject-prefix 'PATCH 6.17.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc(a)google.com>
Date: Thu, 16 Oct 2025 11:21:47 -0700
Subject: [PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or
TDCALL
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD
guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL
is gated by any software enablement other than VMXON, and so will generate
a VM-Exit instead of e.g. a native #UD when executed from the guest kernel.
Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and
SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX
non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a
nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can
crash itself, but not L1.
Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's
pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit,
but that appears to be a documentation bug (likely because the CPL > 0
check was incorrectly bundled with other lower-priority #GP checks).
Testing on SPR and EMR shows that the CPL > 0 check is performed before
the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode.
Note #3! The aforementioned Trust Domain spec uses confusing pseudocode
that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM"
specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long-
form description explicitly states that SEAMCALL generates an exit when
executed in "SEAM VMX non-root operation". But that's a moot point as the
TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as
documented in the "Unconditionally Blocked Instructions" section of the
TDX-Module base specification.
Cc: stable(a)vger.kernel.org
Cc: Kai Huang <kai.huang(a)intel.com>
Cc: Xiaoyao Li <xiaoyao.li(a)intel.com>
Cc: Rick Edgecombe <rick.p.edgecombe(a)intel.com>
Cc: Dan Williams <dan.j.williams(a)intel.com>
Cc: Binbin Wu <binbin.wu(a)linux.intel.com>
Reviewed-by: Kai Huang <kai.huang(a)intel.com>
Reviewed-by: Binbin Wu <binbin.wu(a)linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com>
Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc(a)google.com>
diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index 9792e329343e..1baa86dfe029 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -93,6 +93,7 @@
#define EXIT_REASON_TPAUSE 68
#define EXIT_REASON_BUS_LOCK 74
#define EXIT_REASON_NOTIFY 75
+#define EXIT_REASON_SEAMCALL 76
#define EXIT_REASON_TDCALL 77
#define EXIT_REASON_MSR_READ_IMM 84
#define EXIT_REASON_MSR_WRITE_IMM 85
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 76271962cb70..bcea087b642f 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu,
case EXIT_REASON_NOTIFY:
/* Notify VM exit is not exposed to L1 */
return false;
+ case EXIT_REASON_SEAMCALL:
+ case EXIT_REASON_TDCALL:
+ /*
+ * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't
+ * virtualized by KVM for L1 hypervisors, i.e. L1 should
+ * never want or expect such an exit.
+ */
+ return false;
default:
return true;
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f87c216d976d..91b6f2f3edc2 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6032,6 +6032,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu)
return 1;
}
+static int handle_tdx_instruction(struct kvm_vcpu *vcpu)
+{
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return 1;
+}
+
#ifndef CONFIG_X86_SGX_KVM
static int handle_encls(struct kvm_vcpu *vcpu)
{
@@ -6157,6 +6163,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
[EXIT_REASON_ENCLS] = handle_encls,
[EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit,
[EXIT_REASON_NOTIFY] = handle_notify,
+ [EXIT_REASON_SEAMCALL] = handle_tdx_instruction,
+ [EXIT_REASON_TDCALL] = handle_tdx_instruction,
[EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm,
[EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm,
};
In btusb_mtk_setup(), we set `btmtk_data->isopkt_intf` to:
usb_ifnum_to_if(data->udev, MTK_ISO_IFNUM)
That function can return NULL in some cases. Even when it returns
NULL, though, we still go on to call btusb_mtk_claim_iso_intf().
As of commit e9087e828827 ("Bluetooth: btusb: mediatek: Add locks for
usb_driver_claim_interface()"), calling btusb_mtk_claim_iso_intf()
when `btmtk_data->isopkt_intf` is NULL will cause a crash because
we'll end up passing a bad pointer to device_lock(). Prior to that
commit we'd pass the NULL pointer directly to
usb_driver_claim_interface() which would detect it and return an
error, which was handled.
Resolve the crash in btusb_mtk_claim_iso_intf() by adding a NULL check
at the start of the function. This makes the code handle a NULL
`btmtk_data->isopkt_intf` the same way it did before the problematic
commit (just with a slight change to the error message printed).
Reported-by: IncogCyberpunk <incogcyberpunk(a)proton.me>
Closes: http://lore.kernel.org/r/a380d061-479e-4713-bddd-1d6571ca7e86@leemhuis.info
Fixes: e9087e828827 ("Bluetooth: btusb: mediatek: Add locks for usb_driver_claim_interface()")
Cc: stable(a)vger.kernel.org
Tested-by: IncogCyberpunk <incogcyberpunk(a)proton.me>
Signed-off-by: Douglas Anderson <dianders(a)chromium.org>
---
Changes in v3:
- Added Cc to stable.
- Added IncogCyberpunk Tested-by tag.
- v2: https://patch.msgid.link/20251119092641.v2.1.I1ae7aebc967e52c7c4be7aa65fbd8…
Changes in v2:
- Rebase atop commit 529ac8e706c3 ("Bluetooth: ... mtk iso interface")
- v1: https://patch.msgid.link/20251119085354.1.I1ae7aebc967e52c7c4be7aa65fbd8173…
drivers/bluetooth/btusb.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index fcc62e2fb641..683ac02e964b 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -2751,6 +2751,11 @@ static void btusb_mtk_claim_iso_intf(struct btusb_data *data)
if (!btmtk_data)
return;
+ if (!btmtk_data->isopkt_intf) {
+ bt_dev_err(data->hdev, "Can't claim NULL iso interface");
+ return;
+ }
+
/*
* The function usb_driver_claim_interface() is documented to need
* locks held if it's not called from a probe routine. The code here
--
2.52.0.rc1.455.g30608eb744-goog
The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x fa04f5b60fda62c98a53a60de3a1e763f11feb41
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112038-designate-amino-d210@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From fa04f5b60fda62c98a53a60de3a1e763f11feb41 Mon Sep 17 00:00:00 2001
From: Kiryl Shutsemau <kas(a)kernel.org>
Date: Mon, 27 Oct 2025 11:56:36 +0000
Subject: [PATCH] mm/truncate: unmap large folio on split failure
Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are
supposed to generate SIGBUS.
This behavior might not be respected on truncation.
During truncation, the kernel splits a large folio in order to reclaim
memory. As a side effect, it unmaps the folio and destroys PMD mappings
of the folio. The folio will be refaulted as PTEs and SIGBUS semantics
are preserved.
However, if the split fails, PMD mappings are preserved and the user will
not receive SIGBUS on any accesses within the PMD.
Unmap the folio on split failure. It will lead to refault as PTEs and
preserve SIGBUS semantics.
Make an exception for shmem/tmpfs that for long time intentionally mapped
with PMDs across i_size.
Link: https://lkml.kernel.org/r/20251027115636.82382-3-kirill@shutemov.name
Fixes: b9a8a4195c7d ("truncate,shmem: Handle truncates that split large folios")
Signed-off-by: Kiryl Shutsemau <kas(a)kernel.org>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: "Darrick J. Wong" <djwong(a)kernel.org>
Cc: Dave Chinner <david(a)fromorbit.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Hugh Dickins <hughd(a)google.com>
Cc: Johannes Weiner <hannes(a)cmpxchg.org>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mike Rapoport <rppt(a)kernel.org>
Cc: Rik van Riel <riel(a)surriel.com>
Cc: Shakeel Butt <shakeel.butt(a)linux.dev>
Cc: Suren Baghdasaryan <surenb(a)google.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/truncate.c b/mm/truncate.c
index 9210cf808f5c..3c5a50ae3274 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -177,6 +177,32 @@ int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
return 0;
}
+static int try_folio_split_or_unmap(struct folio *folio, struct page *split_at,
+ unsigned long min_order)
+{
+ enum ttu_flags ttu_flags =
+ TTU_SYNC |
+ TTU_SPLIT_HUGE_PMD |
+ TTU_IGNORE_MLOCK;
+ int ret;
+
+ ret = try_folio_split_to_order(folio, split_at, min_order);
+
+ /*
+ * If the split fails, unmap the folio, so it will be refaulted
+ * with PTEs to respect SIGBUS semantics.
+ *
+ * Make an exception for shmem/tmpfs that for long time
+ * intentionally mapped with PMDs across i_size.
+ */
+ if (ret && !shmem_mapping(folio->mapping)) {
+ try_to_unmap(folio, ttu_flags);
+ WARN_ON(folio_mapped(folio));
+ }
+
+ return ret;
+}
+
/*
* Handle partial folios. The folio may be entirely within the
* range if a split has raced with us. If not, we zero the part of the
@@ -226,7 +252,7 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
min_order = mapping_min_folio_order(folio->mapping);
split_at = folio_page(folio, PAGE_ALIGN_DOWN(offset) / PAGE_SIZE);
- if (!try_folio_split_to_order(folio, split_at, min_order)) {
+ if (!try_folio_split_or_unmap(folio, split_at, min_order)) {
/*
* try to split at offset + length to make sure folios within
* the range can be dropped, especially to avoid memory waste
@@ -250,13 +276,10 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
if (!folio_trylock(folio2))
goto out;
- /*
- * make sure folio2 is large and does not change its mapping.
- * Its split result does not matter here.
- */
+ /* make sure folio2 is large and does not change its mapping */
if (folio_test_large(folio2) &&
folio2->mapping == folio->mapping)
- try_folio_split_to_order(folio2, split_at2, min_order);
+ try_folio_split_or_unmap(folio2, split_at2, min_order);
folio_unlock(folio2);
out:
The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 74207de2ba10c2973334906822dc94d2e859ffc5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112025-voucher-hexagram-61bf@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 74207de2ba10c2973334906822dc94d2e859ffc5 Mon Sep 17 00:00:00 2001
From: Kiryl Shutsemau <kas(a)kernel.org>
Date: Mon, 27 Oct 2025 11:56:35 +0000
Subject: [PATCH] mm/memory: do not populate page table entries beyond i_size
Patch series "Fix SIGBUS semantics with large folios", v3.
Accessing memory within a VMA, but beyond i_size rounded up to the next
page size, is supposed to generate SIGBUS.
Darrick reported[1] an xfstests regression in v6.18-rc1. generic/749
failed due to missing SIGBUS. This was caused by my recent changes that
try to fault in the whole folio where possible:
19773df031bc ("mm/fault: try to map the entire file folio in finish_fault()")
357b92761d94 ("mm/filemap: map entire large folio faultaround")
These changes did not consider i_size when setting up PTEs, leading to
xfstest breakage.
However, the problem has been present in the kernel for a long time -
since huge tmpfs was introduced in 2016. The kernel happily maps
PMD-sized folios as PMD without checking i_size. And huge=always tmpfs
allocates PMD-size folios on any writes.
I considered this corner case when I implemented a large tmpfs, and my
conclusion was that no one in their right mind should rely on receiving a
SIGBUS signal when accessing beyond i_size. I cannot imagine how it could
be useful for the workload.
But apparently filesystem folks care a lot about preserving strict SIGBUS
semantics.
Generic/749 was introduced last year with reference to POSIX, but no real
workloads were mentioned. It also acknowledged the tmpfs deviation from
the test case.
POSIX indeed says[3]:
References within the address range starting at pa and
continuing for len bytes to whole pages following the end of an
object shall result in delivery of a SIGBUS signal.
The patchset fixes the regression introduced by recent changes as well as
more subtle SIGBUS breakage due to split failure on truncation.
This patch (of 2):
Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are
supposed to generate SIGBUS.
Recent changes attempted to fault in full folio where possible. They did
not respect i_size, which led to populating PTEs beyond i_size and
breaking SIGBUS semantics.
Darrick reported generic/749 breakage because of this.
However, the problem existed before the recent changes. With huge=always
tmpfs, any write to a file leads to PMD-size allocation. Following the
fault-in of the folio will install PMD mapping regardless of i_size.
Fix filemap_map_pages() and finish_fault() to not install:
- PTEs beyond i_size;
- PMD mappings across i_size;
Make an exception for shmem/tmpfs that for long time intentionally
mapped with PMDs across i_size.
Link: https://lkml.kernel.org/r/20251027115636.82382-1-kirill@shutemov.name
Link: https://lkml.kernel.org/r/20251027115636.82382-2-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas(a)kernel.org>
Fixes: 6795801366da ("xfs: Support large folios")
Reported-by: "Darrick J. Wong" <djwong(a)kernel.org>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: Dave Chinner <david(a)fromorbit.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Hugh Dickins <hughd(a)google.com>
Cc: Johannes Weiner <hannes(a)cmpxchg.org>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mike Rapoport <rppt(a)kernel.org>
Cc: Rik van Riel <riel(a)surriel.com>
Cc: Shakeel Butt <shakeel.butt(a)linux.dev>
Cc: Suren Baghdasaryan <surenb(a)google.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index 13f0259d993c..2f1e7e283a51 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3681,7 +3681,8 @@ static struct folio *next_uptodate_folio(struct xa_state *xas,
static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
struct folio *folio, unsigned long start,
unsigned long addr, unsigned int nr_pages,
- unsigned long *rss, unsigned short *mmap_miss)
+ unsigned long *rss, unsigned short *mmap_miss,
+ bool can_map_large)
{
unsigned int ref_from_caller = 1;
vm_fault_t ret = 0;
@@ -3696,7 +3697,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
* The folio must not cross VMA or page table boundary.
*/
addr0 = addr - start * PAGE_SIZE;
- if (folio_within_vma(folio, vmf->vma) &&
+ if (can_map_large && folio_within_vma(folio, vmf->vma) &&
(addr0 & PMD_MASK) == ((addr0 + folio_size(folio) - 1) & PMD_MASK)) {
vmf->pte -= start;
page -= start;
@@ -3811,13 +3812,27 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
unsigned long rss = 0;
unsigned int nr_pages = 0, folio_type;
unsigned short mmap_miss = 0, mmap_miss_saved;
+ bool can_map_large;
rcu_read_lock();
folio = next_uptodate_folio(&xas, mapping, end_pgoff);
if (!folio)
goto out;
- if (filemap_map_pmd(vmf, folio, start_pgoff)) {
+ file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1;
+ end_pgoff = min(end_pgoff, file_end);
+
+ /*
+ * Do not allow to map with PTEs beyond i_size and with PMD
+ * across i_size to preserve SIGBUS semantics.
+ *
+ * Make an exception for shmem/tmpfs that for long time
+ * intentionally mapped with PMDs across i_size.
+ */
+ can_map_large = shmem_mapping(mapping) ||
+ file_end >= folio_next_index(folio);
+
+ if (can_map_large && filemap_map_pmd(vmf, folio, start_pgoff)) {
ret = VM_FAULT_NOPAGE;
goto out;
}
@@ -3830,10 +3845,6 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
goto out;
}
- file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1;
- if (end_pgoff > file_end)
- end_pgoff = file_end;
-
folio_type = mm_counter_file(folio);
do {
unsigned long end;
@@ -3850,7 +3861,8 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
else
ret |= filemap_map_folio_range(vmf, folio,
xas.xa_index - folio->index, addr,
- nr_pages, &rss, &mmap_miss);
+ nr_pages, &rss, &mmap_miss,
+ can_map_large);
folio_unlock(folio);
} while ((folio = next_uptodate_folio(&xas, mapping, end_pgoff)) != NULL);
diff --git a/mm/memory.c b/mm/memory.c
index 74b45e258323..b59ae7ce42eb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -65,6 +65,7 @@
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/string.h>
+#include <linux/shmem_fs.h>
#include <linux/memory-tiers.h>
#include <linux/debugfs.h>
#include <linux/userfaultfd_k.h>
@@ -5501,8 +5502,25 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
return ret;
}
+ if (!needs_fallback && vma->vm_file) {
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ pgoff_t file_end;
+
+ file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
+
+ /*
+ * Do not allow to map with PTEs beyond i_size and with PMD
+ * across i_size to preserve SIGBUS semantics.
+ *
+ * Make an exception for shmem/tmpfs that for long time
+ * intentionally mapped with PMDs across i_size.
+ */
+ needs_fallback = !shmem_mapping(mapping) &&
+ file_end < folio_next_index(folio);
+ }
+
if (pmd_none(*vmf->pmd)) {
- if (folio_test_pmd_mappable(folio)) {
+ if (!needs_fallback && folio_test_pmd_mappable(folio)) {
ret = do_set_pmd(vmf, folio, page);
if (ret != VM_FAULT_FALLBACK)
return ret;