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authorDmitry Safonov <dima@arista.com>2020-12-14 19:08:21 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-15 12:13:41 -0800
commit73d5e06299195f4df82832cfc4a3a0c574c1e473 (patch)
treed2923cc106b9f374e309b8760e4e5d9927b998fd /mm
parentdd3b614f858d88f33e0cf8b7353e2ad937e71da3 (diff)
mremap: check if it's possible to split original vma
If original VMA can't be split at the desired address, do_munmap() will fail and leave both new-copied VMA and old VMA. De-facto it's MREMAP_DONTUNMAP behaviour, which is unexpected. Currently, it may fail such way for hugetlbfs and dax device mappings. Minimize such unpleasant situations to OOM by checking .may_split() before attempting to create a VMA copy. Link: https://lkml.kernel.org/r/20201013013416.390574-6-dima@arista.com Signed-off-by: Dmitry Safonov <dima@arista.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andy Lutomirski <luto@kernel.org> Cc: Brian Geffon <bgeffon@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mremap.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 366b3dea992c..c5590afe7165 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -493,7 +493,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
unsigned long excess = 0;
unsigned long hiwater_vm;
int split = 0;
- int err;
+ int err = 0;
bool need_rmap_locks;
/*
@@ -503,6 +503,15 @@ static unsigned long move_vma(struct vm_area_struct *vma,
if (mm->map_count >= sysctl_max_map_count - 3)
return -ENOMEM;
+ if (vma->vm_ops && vma->vm_ops->may_split) {
+ if (vma->vm_start != old_addr)
+ err = vma->vm_ops->may_split(vma, old_addr);
+ if (!err && vma->vm_end != old_addr + old_len)
+ err = vma->vm_ops->may_split(vma, old_addr + old_len);
+ if (err)
+ return err;
+ }
+
/*
* Advise KSM to break any KSM pages in the area to be moved:
* it would be confusing if they were to turn up at the new