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| author | Dmitry Safonov <dima@arista.com> | 2020-12-14 19:08:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 12:13:41 -0800 |
| commit | 73d5e06299195f4df82832cfc4a3a0c574c1e473 (patch) | |
| tree | d2923cc106b9f374e309b8760e4e5d9927b998fd /mm | |
| parent | dd3b614f858d88f33e0cf8b7353e2ad937e71da3 (diff) | |
| download | lwn-73d5e06299195f4df82832cfc4a3a0c574c1e473.tar.gz lwn-73d5e06299195f4df82832cfc4a3a0c574c1e473.zip | |
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.c | 11 |
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 |