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charset="utf-8" Consider the case of a a partial mremap() (that results in a VMA split) of an accountable VMA (i.e. which has the VM_ACCOUNT flag set) whose start address is zero, with the MREMAP_MAYMOVE flag specified and a scenario where a move does in fact occur: addr end | | v v |-------------| | vma | |-------------| 0 This move is affected by unmapping the range [addr, end). In order to prevent an incorrect decrement of accounted memory which has already been determined, the mremap() code in move_vma() clears VM_ACCOUNT from the VMA prior to doing so, before reestablishing it in each of the VMAs post-split: addr end | | v v |---| |---| | A | | B | |---| |---| Commit 6b73cff239e5 ("mm: change munmap splitting order and move_vma()") changed this logic such as to determine whether there is a need to do so by establishing account_start and account_end and, in the instance where such an operation is required, assigning them to vma->vm_start and vma->vm_end. Later the code checks if the operation is required for 'A' referenced above thusly: if (account_start) { ... } However, if the VMA described above has vma->vm_start =3D=3D 0, which is now assigned to account_start, this branch will not be executed. As a result, the VMA 'A' above will remain stripped of its VM_ACCOUNT flag, incorrectly. The fix is to simply convert these variables to booleans and set them as required. Signed-off-by: Lorenzo Stoakes Fixes: 6b73cff239e5 ("mm: change munmap splitting order and move_vma()") Cc: stable@vger.kernel.org Reviewed-by: Harry Yoo Reviewed-by: Liam R. Howlett Reviewed-by: Vlastimil Babka --- mm/mremap.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index cff7f552f909..c3e4c86d0b8d 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -705,8 +705,8 @@ static unsigned long move_vma(struct vm_area_struct *vm= a, unsigned long vm_flags =3D vma->vm_flags; unsigned long new_pgoff; unsigned long moved_len; - unsigned long account_start =3D 0; - unsigned long account_end =3D 0; + bool account_start =3D false; + bool account_end =3D false; unsigned long hiwater_vm; int err =3D 0; bool need_rmap_locks; @@ -790,9 +790,9 @@ static unsigned long move_vma(struct vm_area_struct *vm= a, if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) { vm_flags_clear(vma, VM_ACCOUNT); if (vma->vm_start < old_addr) - account_start =3D vma->vm_start; + account_start =3D true; if (vma->vm_end > old_addr + old_len) - account_end =3D vma->vm_end; + account_end =3D true; } =20 /* @@ -832,7 +832,7 @@ static unsigned long move_vma(struct vm_area_struct *vm= a, /* OOM: unable to split vma, just get accounts right */ if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) vm_acct_memory(old_len >> PAGE_SHIFT); - account_start =3D account_end =3D 0; + account_start =3D account_end =3D false; } =20 if (vm_flags & VM_LOCKED) { --=20 2.48.1