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authorJan Kara <jack@suse.cz>2009-06-09 16:26:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-09 16:59:03 -0700
commita61d90d75d0f9e86432c45b496b4b0fbf0fd03dc (patch)
tree85d557e9d67cbad0347c6f12f7a60c474e485f7c
parent463aea1a1c49f1a7d4b50656dfd6c8bb33358b1b (diff)
downloadop-kernel-dev-a61d90d75d0f9e86432c45b496b4b0fbf0fd03dc.zip
op-kernel-dev-a61d90d75d0f9e86432c45b496b4b0fbf0fd03dc.tar.gz
jbd: fix race in buffer processing in commit code
In commit code, we scan buffers attached to a transaction. During this scan, we sometimes have to drop j_list_lock and then we recheck whether the journal buffer head didn't get freed by journal_try_to_free_buffers(). But checking for buffer_jbd(bh) isn't enough because a new journal head could get attached to our buffer head. So add a check whether the journal head remained the same and whether it's still at the same transaction and list. This is a nasty bug and can cause problems like memory corruption (use after free) or trigger various assertions in JBD code (observed). Signed-off-by: Jan Kara <jack@suse.cz> Cc: <stable@kernel.org> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/jbd/commit.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 06560c5..618e21c 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -241,7 +241,7 @@ write_out_data:
spin_lock(&journal->j_list_lock);
}
/* Someone already cleaned up the buffer? */
- if (!buffer_jbd(bh)
+ if (!buffer_jbd(bh) || bh2jh(bh) != jh
|| jh->b_transaction != commit_transaction
|| jh->b_jlist != BJ_SyncData) {
jbd_unlock_bh_state(bh);
@@ -478,7 +478,9 @@ void journal_commit_transaction(journal_t *journal)
spin_lock(&journal->j_list_lock);
continue;
}
- if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
+ if (buffer_jbd(bh) && bh2jh(bh) == jh &&
+ jh->b_transaction == commit_transaction &&
+ jh->b_jlist == BJ_Locked) {
__journal_unfile_buffer(jh);
jbd_unlock_bh_state(bh);
journal_remove_journal_head(bh);
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