Commit 31f2b0eb authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

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: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarRik 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 93b4a44f
...@@ -133,8 +133,8 @@ int anon_vma_prepare(struct vm_area_struct *vma) ...@@ -133,8 +133,8 @@ int anon_vma_prepare(struct vm_area_struct *vma)
goto out_enomem_free_avc; goto out_enomem_free_avc;
allocated = anon_vma; allocated = anon_vma;
} }
spin_lock(&anon_vma->lock);
spin_lock(&anon_vma->lock);
/* page_table_lock to protect against threads */ /* page_table_lock to protect against threads */
spin_lock(&mm->page_table_lock); spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) { if (likely(!vma->anon_vma)) {
...@@ -144,14 +144,15 @@ int anon_vma_prepare(struct vm_area_struct *vma) ...@@ -144,14 +144,15 @@ int anon_vma_prepare(struct vm_area_struct *vma)
list_add(&avc->same_vma, &vma->anon_vma_chain); list_add(&avc->same_vma, &vma->anon_vma_chain);
list_add(&avc->same_anon_vma, &anon_vma->head); list_add(&avc->same_anon_vma, &anon_vma->head);
allocated = NULL; allocated = NULL;
avc = NULL;
} }
spin_unlock(&mm->page_table_lock); spin_unlock(&mm->page_table_lock);
spin_unlock(&anon_vma->lock); spin_unlock(&anon_vma->lock);
if (unlikely(allocated)) {
if (unlikely(allocated))
anon_vma_free(allocated); anon_vma_free(allocated);
if (unlikely(avc))
anon_vma_chain_free(avc); anon_vma_chain_free(avc);
}
} }
return 0; return 0;
......
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