Incorrect invocation of VMA callbacks when the VMA is no longer in a consistent state is bug prone and risky to perform.
With regards to the important vm_ops->close() callback We have gone to great lengths to try to track whether or not we ought to close VMAs.
Rather than doing so and risking making a mistake somewhere, instead unconditionally close and reset vma->vm_ops to an empty dummy operations set with a NULL .close operator.
We introduce a new function to do so - vma_close() - and simplify existing vms logic which tracked whether we needed to close or not.
This simplifies the logic, avoids incorrect double-calling of the .close() callback and allows us to update error paths to simply call vma_close() unconditionally - making VMA closure idempotent.
Link: https://lkml.kernel.org/r/28e89dda96f68c505cb6f8e9fc9b57c3e9f74b42.173022466... Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails") Signed-off-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Reported-by: Jann Horn jannh@google.com Reviewed-by: Vlastimil Babka vbabka@suse.cz Reviewed-by: Liam R. Howlett Liam.Howlett@oracle.com Reviewed-by: Jann Horn jannh@google.com Cc: Andreas Larsson andreas@gaisler.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: David S. Miller davem@davemloft.net Cc: Helge Deller deller@gmx.de Cc: James E.J. Bottomley James.Bottomley@HansenPartnership.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Mark Brown broonie@kernel.org Cc: Peter Xu peterx@redhat.com Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org (cherry picked from commit 4080ef1579b2413435413988d14ac8c68e4d42c8) --- mm/internal.h | 7 +++++++ mm/mmap.c | 9 +++------ mm/nommu.c | 3 +-- mm/util.c | 15 +++++++++++++++ 4 files changed, 26 insertions(+), 8 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h index e47f112a63d3..df2b1156ef65 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -46,6 +46,13 @@ void page_writeback_init(void); */ int mmap_file(struct file *file, struct vm_area_struct *vma);
+/* + * If the VMA has a close hook then close it, and since closing it might leave + * it in an inconsistent state which makes the use of any hooks suspect, clear + * them down by installing dummy empty hooks. + */ +void vma_close(struct vm_area_struct *vma); + vm_fault_t do_swap_page(struct vm_fault *vmf);
void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma, diff --git a/mm/mmap.c b/mm/mmap.c index f4eac5a95d64..ac1517a96066 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -176,8 +176,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) struct vm_area_struct *next = vma->vm_next;
might_sleep(); - if (vma->vm_ops && vma->vm_ops->close) - vma->vm_ops->close(vma); + vma_close(vma); if (vma->vm_file) fput(vma->vm_file); mpol_put(vma_policy(vma)); @@ -1901,8 +1900,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, return addr;
close_and_free_vma: - if (vma->vm_ops && vma->vm_ops->close) - vma->vm_ops->close(vma); + vma_close(vma); unmap_and_free_vma: vma->vm_file = NULL; fput(file); @@ -2788,8 +2786,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, return 0;
/* Clean everything up if vma_adjust failed. */ - if (new->vm_ops && new->vm_ops->close) - new->vm_ops->close(new); + vma_close(new); if (new->vm_file) fput(new->vm_file); unlink_anon_vmas(new); diff --git a/mm/nommu.c b/mm/nommu.c index fdacc3d119c3..f46a883e93e4 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -662,8 +662,7 @@ static void delete_vma_from_mm(struct vm_area_struct *vma) */ static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma) { - if (vma->vm_ops && vma->vm_ops->close) - vma->vm_ops->close(vma); + vma_close(vma); if (vma->vm_file) fput(vma->vm_file); put_nommu_region(vma->vm_region); diff --git a/mm/util.c b/mm/util.c index 8e5bd2c9f4b4..9e0c86555adf 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1091,3 +1091,18 @@ int mmap_file(struct file *file, struct vm_area_struct *vma)
return err; } + +void vma_close(struct vm_area_struct *vma) +{ + static const struct vm_operations_struct dummy_vm_ops = {}; + + if (vma->vm_ops && vma->vm_ops->close) { + vma->vm_ops->close(vma); + + /* + * The mapping is in an inconsistent state, and no further hooks + * may be invoked upon it. + */ + vma->vm_ops = &dummy_vm_ops; + } +}