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authorJan Stancek <jstancek@redhat.com>2013-04-08 13:00:02 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-04-12 09:38:47 -0700
commitcdc8958a19b38773292cb6916f77f1e3bdf6d0fc (patch)
treea60e744f239db71d4bc7fcc687a0ceebbbe1b638 /mm
parent5592a94b44df6e6d48e34cfe596844637a2976ac (diff)
downloadlinux-linaro-stable-cdc8958a19b38773292cb6916f77f1e3bdf6d0fc.tar.gz
mm: prevent mmap_cache race in find_vma()
commit b6a9b7f6b1f21735a7456d534dc0e68e61359d2c upstream. find_vma() can be called by multiple threads with read lock held on mm->mmap_sem and any of them can update mm->mmap_cache. Prevent compiler from re-fetching mm->mmap_cache, because other readers could update it in the meantime: thread 1 thread 2 | find_vma() | find_vma() struct vm_area_struct *vma = NULL; | vma = mm->mmap_cache; | if (!(vma && vma->vm_end > addr | && vma->vm_start <= addr)) { | | mm->mmap_cache = vma; return vma; | ^^ compiler may optimize this | local variable out and re-read | mm->mmap_cache | This issue can be reproduced with gcc-4.8.0-1 on s390x by running mallocstress testcase from LTP, which triggers: kernel BUG at mm/rmap.c:1088! Call Trace: ([<000003d100c57000>] 0x3d100c57000) [<000000000023a1c0>] do_wp_page+0x2fc/0xa88 [<000000000023baae>] handle_pte_fault+0x41a/0xac8 [<000000000023d832>] handle_mm_fault+0x17a/0x268 [<000000000060507a>] do_protection_exception+0x1e2/0x394 [<0000000000603a04>] pgm_check_handler+0x138/0x13c [<000003fffcf1f07a>] 0x3fffcf1f07a Last Breaking-Event-Address: [<000000000024755e>] page_add_new_anon_rmap+0xc2/0x168 Thanks to Jakub Jelinek for his insight on gcc and helping to track this down. Signed-off-by: Jan Stancek <jstancek@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: adjust context, indentation] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c2
-rw-r--r--mm/nommu.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 848ef52d9603..2add0a1a7aa6 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1619,7 +1619,7 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
if (mm) {
/* Check the cache first. */
/* (Cache hit rate is typically around 35%.) */
- vma = mm->mmap_cache;
+ vma = ACCESS_ONCE(mm->mmap_cache);
if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
struct rb_node * rb_node;
diff --git a/mm/nommu.c b/mm/nommu.c
index bb8f4f004a82..b0956e39fd1c 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -807,7 +807,7 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
struct vm_area_struct *vma;
/* check the cache first */
- vma = mm->mmap_cache;
+ vma = ACCESS_ONCE(mm->mmap_cache);
if (vma && vma->vm_start <= addr && vma->vm_end > addr)
return vma;