[PATCH 6.3 01/29] mm/mmap: Fix error path in do_vmi_align_munmap()

Greg Kroah-Hartman
2023-06-29T18:46:07Z

From: "Liam R. Howlett" <Liam.Howlett@oracle.com>

commit 606c812eb1d5b5fb0dd9e330ca94b52d7c227830 upstream.

The error unrolling was leaving the VMAs detached in many cases and
leaving the locked_vm statistic altered, and skipping the unrolling
entirely in the case of the vma tree write failing.

Fix the error path by re-attaching the detached VMAs and adding the
necessary goto for the failed vma tree write, and fix the locked_vm
statistic by only updating after the vma tree write succeeds.

Fixes: 763ecb035029 ("mm: remove the vma linked list")
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ dwmw2: Strictly, the original patch wasn't *re-attaching* the
detached VMAs. They *were* still attached but just had
the 'detached' flag set, which is an optimisation. Which
doesn't exist in 6.3, so drop that. Also drop the call
to vma_start_write() which came in with the per-VMA
locking in 6.4. ]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/mmap.c | 29 +++++++++++------------------
1 file changed, 11 insertions(+), 18 deletions(-)

--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2280,19 +2280,6 @@ int split_vma(struct vma_iterator *vmi,
return __split_vma(vmi, vma, addr, new_below);
}

-static inline int munmap_sidetree(struct vm_area_struct *vma,
- struct ma_state *mas_detach)
-{
- mas_set_range(mas_detach, vma->vm_start, vma->vm_end - 1);
- if (mas_store_gfp(mas_detach, vma, GFP_KERNEL))
- return -ENOMEM;
-
- if (vma->vm_flags & VM_LOCKED)
- vma->vm_mm->locked_vm -= vma_pages(vma);
-
- return 0;
-}
-
/*
* do_vmi_align_munmap() - munmap the aligned region from @start to @end.
* @vmi: The vma iterator
@@ -2314,6 +2301,7 @@ do_vmi_align_munmap(struct vma_iterator
struct maple_tree mt_detach;
int count = 0;
int error = -ENOMEM;
+ unsigned long locked_vm = 0;
MA_STATE(mas_detach, &mt_detach, 0, 0);
mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
mt_set_external_lock(&mt_detach, &mm->mmap_lock);
@@ -2359,9 +2347,11 @@ do_vmi_align_munmap(struct vma_iterator
if (error)
goto end_split_failed;
}
- error = munmap_sidetree(next, &mas_detach);
- if (error)
- goto munmap_sidetree_failed;
+ mas_set_range(&mas_detach, next->vm_start, next->vm_end - 1);
+ if (mas_store_gfp(&mas_detach, next, GFP_KERNEL))
+ goto munmap_gather_failed;
+ if (next->vm_flags & VM_LOCKED)
+ locked_vm += vma_pages(next);

count++;
#ifdef CONFIG_DEBUG_VM_MAPLE_TREE
@@ -2407,10 +2397,12 @@ do_vmi_align_munmap(struct vma_iterator
}
#endif
/* Point of no return */
+ error = -ENOMEM;
vma_iter_set(vmi, start);
if (vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL))
- return -ENOMEM;
+ goto clear_tree_failed;

+ mm->locked_vm -= locked_vm;
mm->map_count -= count;
/*
* Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
@@ -2440,8 +2432,9 @@ do_vmi_align_munmap(struct vma_iterator
validate_mm(mm);
return downgrade ? 1 : 0;

+clear_tree_failed:
userfaultfd_error:
-munmap_sidetree_failed:
+munmap_gather_failed:
end_split_failed:
__mt_destroy(&mt_detach);