The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x ce56d21355cd6f6937aca32f1f44ca749d1e4808 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023112447-veto-frail-2fa8@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
ce56d21355cd ("ext4: fix racy may inline data check in dio write") 310ee0902b8d ("ext4: allow concurrent unaligned dio overwrites") 240930fb7e6b ("ext4: dio take shared inode lock when overwriting preallocated blocks")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From ce56d21355cd6f6937aca32f1f44ca749d1e4808 Mon Sep 17 00:00:00 2001 From: Brian Foster bfoster@redhat.com Date: Mon, 2 Oct 2023 14:50:20 -0400 Subject: [PATCH] ext4: fix racy may inline data check in dio write
syzbot reports that the following warning from ext4_iomap_begin() triggers as of the commit referenced below:
if (WARN_ON_ONCE(ext4_has_inline_data(inode))) return -ERANGE;
This occurs during a dio write, which is never expected to encounter an inode with inline data. To enforce this behavior, ext4_dio_write_iter() checks the current inline state of the inode and clears the MAY_INLINE_DATA state flag to either fall back to buffered writes, or enforce that any other writers in progress on the inode are not allowed to create inline data.
The problem is that the check for existing inline data and the state flag can span a lock cycle. For example, if the ilock is originally locked shared and subsequently upgraded to exclusive, another writer may have reacquired the lock and created inline data before the dio write task acquires the lock and proceeds.
The commit referenced below loosens the lock requirements to allow some forms of unaligned dio writes to occur under shared lock, but AFAICT the inline data check was technically already racy for any dio write that would have involved a lock cycle. Regardless, lift clearing of the state bit to the same lock critical section that checks for preexisting inline data on the inode to close the race.
Cc: stable@kernel.org Reported-by: syzbot+307da6ca5cb0d01d581a@syzkaller.appspotmail.com Fixes: 310ee0902b8d ("ext4: allow concurrent unaligned dio overwrites") Signed-off-by: Brian Foster bfoster@redhat.com Link: https://lore.kernel.org/r/20231002185020.531537-1-bfoster@redhat.com Signed-off-by: Theodore Ts'o tytso@mit.edu
diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 6830ea3a6c59..747c0378122d 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -569,18 +569,20 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from) return ext4_buffered_write_iter(iocb, from); }
+ /* + * Prevent inline data from being created since we are going to allocate + * blocks for DIO. We know the inode does not currently have inline data + * because ext4_should_use_dio() checked for it, but we have to clear + * the state flag before the write checks because a lock cycle could + * introduce races with other writers. + */ + ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA); + ret = ext4_dio_write_checks(iocb, from, &ilock_shared, &extend, &unwritten, &dio_flags); if (ret <= 0) return ret;
- /* - * Make sure inline data cannot be created anymore since we are going - * to allocate blocks for DIO. We know the inode does not have any - * inline data now because ext4_dio_supported() checked for that. - */ - ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA); - offset = iocb->ki_pos; count = ret;