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authornpiggin@suse.de <npiggin@suse.de>2010-06-24 13:02:14 +1000
committerLinus Torvalds <torvalds@linux-foundation.org>2010-06-29 10:38:22 -0700
commit57439f878afafefad8836ebf5c49da2a0a746105 (patch)
treeec11dd35704aa37d77a5fd8404fda57f297a3834 /fs
parent5904b3b81d25166e5e39b9727645bb47937618e3 (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.c2
-rw-r--r--fs/super.c6
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);