| From: Theodore Ts'o <tytso@mit.edu> |
| Date: Wed, 18 Apr 2018 11:49:31 -0400 |
| Subject: ext4: set h_journal if there is a failure starting a reserved handle |
| |
| commit b2569260d55228b617bd82aba6d0db2faeeb4116 upstream. |
| |
| If ext4 tries to start a reserved handle via |
| jbd2_journal_start_reserved(), and the journal has been aborted, this |
| can result in a NULL pointer dereference. This is because the fields |
| h_journal and h_transaction in the handle structure share the same |
| memory, via a union, so jbd2_journal_start_reserved() will clear |
| h_journal before calling start_this_handle(). If this function fails |
| due to an aborted handle, h_journal will still be NULL, and the call |
| to jbd2_journal_free_reserved() will pass a NULL journal to |
| sub_reserve_credits(). |
| |
| This can be reproduced by running "kvm-xfstests -c dioread_nolock |
| generic/475". |
| |
| Fixes: 8f7d89f36829b ("jbd2: transaction reservation support") |
| Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
| Reviewed-by: Andreas Dilger <adilger@dilger.ca> |
| Reviewed-by: Jan Kara <jack@suse.cz> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| fs/jbd2/transaction.c | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| --- a/fs/jbd2/transaction.c |
| +++ b/fs/jbd2/transaction.c |
| @@ -515,6 +515,7 @@ int jbd2_journal_start_reserved(handle_t |
| */ |
| ret = start_this_handle(journal, handle, GFP_NOFS); |
| if (ret < 0) { |
| + handle->h_journal = journal; |
| jbd2_journal_free_reserved(handle); |
| return ret; |
| } |
