From 578c20ab383f186f908c5b080ed4562cf850de93 Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Date: Fri, 29 Sep 2023 14:30:39 -0400
Subject: [PATCH] mmap: fix vma_iterator in error path of vma_merge()
commit 1419430c8abb5a00590169068590dd54d86590ba upstream.
During the error path, the vma iterator may not be correctly positioned or
set to the correct range. Undo the vma_prev() call by resetting to the
passed in address. Re-walking to the same range will fix the range to the
area previously passed in.
Users would notice increased cycles as vma_merge() would be called an
extra time with vma == prev, and thus would fail to merge and return.
Link: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20230929183041.2835469-2-Liam.Howlett@oracle.com
Fixes: 18b098af2890 ("vma_merge: set vma iterator to correct position.")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Jann Horn <jannh@google.com>
Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/mmap.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 6d25c619911f..0e2d90057306 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -988,10 +988,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
/* Error in anon_vma clone. */
if (err)
- return NULL;
+ goto anon_vma_fail;
if (vma_iter_prealloc(vmi))
- return NULL;
+ goto prealloc_fail;
init_multi_vma_prep(&vp, vma, adjust, remove, remove2);
VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
@@ -1024,6 +1024,12 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
khugepaged_enter_vma(res, vm_flags);
return res;
+
+prealloc_fail:
+anon_vma_fail:
+ vma_iter_set(vmi, addr);
+ vma_iter_load(vmi);
+ return NULL;
}
/*
--
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