diff options
| author | npiggin@suse.de <npiggin@suse.de> | 2010-06-24 13:02:14 +1000 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-06-29 10:38:22 -0700 |
| commit | 57439f878afafefad8836ebf5c49da2a0a746105 (patch) | |
| tree | ec11dd35704aa37d77a5fd8404fda57f297a3834 /fs | |
| parent | 5904b3b81d25166e5e39b9727645bb47937618e3 (diff) | |
fs: fix superblock iteration race
list_for_each_entry_safe is not suitable to protect against concurrent
modification of the list. 6754af6 introduced a race in sb walking.
list_for_each_entry can use the trick of pinning the current entry in
the list before we drop and retake the lock because it subsequently
follows cur->next. However list_for_each_entry_safe saves n=cur->next
for following before entering the loop body, so when the lock is
dropped, n may be deleted.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Frank Mayhar <fmayhar@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/dcache.c | 2 | ||||
| -rw-r--r-- | fs/super.c | 6 |
2 files changed, 8 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index d96047b4a63..c8c78ba0782 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -590,6 +590,8 @@ static void prune_dcache(int count) up_read(&sb->s_umount); } spin_lock(&sb_lock); + /* lock was dropped, must reset next */ + list_safe_reset_next(sb, n, s_list); count -= pruned; __put_super(sb); /* more work left to do? */ diff --git a/fs/super.c b/fs/super.c index 5c35bc7a499..938119ab8dc 100644 --- a/fs/super.c +++ b/fs/super.c @@ -374,6 +374,8 @@ void sync_supers(void) up_read(&sb->s_umount); spin_lock(&sb_lock); + /* lock was dropped, must reset next */ + list_safe_reset_next(sb, n, s_list); __put_super(sb); } } @@ -405,6 +407,8 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg) up_read(&sb->s_umount); spin_lock(&sb_lock); + /* lock was dropped, must reset next */ + list_safe_reset_next(sb, n, s_list); __put_super(sb); } spin_unlock(&sb_lock); @@ -585,6 +589,8 @@ static void do_emergency_remount(struct work_struct *work) } up_write(&sb->s_umount); spin_lock(&sb_lock); + /* lock was dropped, must reset next */ + list_safe_reset_next(sb, n, s_list); __put_super(sb); } spin_unlock(&sb_lock); |