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authorOleg Nesterov <oleg@redhat.com>2010-04-23 13:18:01 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-04-24 14:31:25 -0400
commit31f2b0ebc01fd332cb0997f7ce9f9cde29af9e20 (patch)
treefc9d4cb410052afcc56bb8442a2dbcb8950464a8 /mm/rmap.c
parent93b4a44f3ad69520d605aace3f3486b8eb754b96 (diff)
rmap: anon_vma_prepare() can leak anon_vma_chain
If find_mergeable_anon_vma() succeeds but another thread installs ->anon_vma before we take ptl, then allocated == NULL but avc should be freed. Change the code to check avc != NULL to detect this case. Also, a couple of whitespace changes to make the critical section more visible. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: Pete Zaitcev <zaitcev@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 526704e8215d..07fc94758799 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -133,8 +133,8 @@ int anon_vma_prepare(struct vm_area_struct *vma)
133 goto out_enomem_free_avc; 133 goto out_enomem_free_avc;
134 allocated = anon_vma; 134 allocated = anon_vma;
135 } 135 }
136 spin_lock(&anon_vma->lock);
137 136
137 spin_lock(&anon_vma->lock);
138 /* page_table_lock to protect against threads */ 138 /* page_table_lock to protect against threads */
139 spin_lock(&mm->page_table_lock); 139 spin_lock(&mm->page_table_lock);
140 if (likely(!vma->anon_vma)) { 140 if (likely(!vma->anon_vma)) {
@@ -144,14 +144,15 @@ int anon_vma_prepare(struct vm_area_struct *vma)
144 list_add(&avc->same_vma, &vma->anon_vma_chain); 144 list_add(&avc->same_vma, &vma->anon_vma_chain);
145 list_add(&avc->same_anon_vma, &anon_vma->head); 145 list_add(&avc->same_anon_vma, &anon_vma->head);
146 allocated = NULL; 146 allocated = NULL;
147 avc = NULL;
147 } 148 }
148 spin_unlock(&mm->page_table_lock); 149 spin_unlock(&mm->page_table_lock);
149
150 spin_unlock(&anon_vma->lock); 150 spin_unlock(&anon_vma->lock);
151 if (unlikely(allocated)) { 151
152 if (unlikely(allocated))
152 anon_vma_free(allocated); 153 anon_vma_free(allocated);
154 if (unlikely(avc))
153 anon_vma_chain_free(avc); 155 anon_vma_chain_free(avc);
154 }
155 } 156 }
156 return 0; 157 return 0;
157 158