The patch titled
Subject: mmap: fix vma_iterator in error path of vma_merge()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mmap-fix-vma_iterator-in-error-path-of-vma_merge.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmap-fix-vma_iterator-in-error-path-of-vma_merge.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Subject: mmap: fix vma_iterator in error path of vma_merge()
Date: Wed, 27 Sep 2023 12:07:44 -0400
When merging of the previous VMA fails after the vma iterator has been
moved to the previous entry, the vma iterator must be advanced to ensure
the caller takes the correct action on the next vma iterator event. Fix
this by adding a vma_next() call to the error path.
Users may experience higher CPU usage, most likely in very low memory
situations.
Link: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@xxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20230927160746.1928098-2-Liam.Howlett@xxxxxxxxxx
Fixes: 18b098af2890 ("vma_merge: set vma iterator to correct position.")
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@xxxxxxxxxxxxxx/
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/mm/mmap.c~mmap-fix-vma_iterator-in-error-path-of-vma_merge
+++ a/mm/mmap.c
@@ -968,14 +968,14 @@ struct vm_area_struct *vma_merge(struct
vma_pgoff = curr->vm_pgoff;
vma_start_write(curr);
remove = curr;
- err = dup_anon_vma(next, curr);
+ err = dup_anon_vma(next, curr, &anon_dup);
}
}
}
/* Error in anon_vma clone. */
if (err)
- return NULL;
+ goto anon_vma_fail;
if (vma_start < vma->vm_start || vma_end > vma->vm_end)
vma_expanded = true;
@@ -988,7 +988,7 @@ struct vm_area_struct *vma_merge(struct
}
if (vma_iter_prealloc(vmi, vma))
- return NULL;
+ goto prealloc_fail;
init_multi_vma_prep(&vp, vma, adjust, remove, remove2);
VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
@@ -1016,6 +1016,12 @@ struct vm_area_struct *vma_merge(struct
vma_complete(&vp, vmi, mm);
khugepaged_enter_vma(res, vm_flags);
return res;
+
+prealloc_fail:
+anon_vma_fail:
+ if (merge_prev)
+ vma_next(vmi);
+ return NULL;
}
/*
_
Patches currently in -mm which might be from Liam.Howlett@xxxxxxxxxx are
maple_tree-add-mas_active-to-detect-in-tree-walks.patch
maple_tree-add-mas_underflow-and-mas_overflow-states.patch
mmap-fix-vma_iterator-in-error-path-of-vma_merge.patch
mmap-fix-error-paths-with-dup_anon_vma.patch
mmap-add-clarifying-comment-to-vma_merge-code.patch
