From: Zhihao Cheng chengzhihao1@huawei.com
mainline inclusion from mainline-v6.12-rc1 commit dda898d7ffe85931f9cca6d702a51f33717c501e category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAU1DM CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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The dax_iomap_rw() does two things in each iteration: map written blocks and copy user data to blocks. If the process is killed by user(See signal handling in dax_iomap_iter()), the copied data will be returned and added on inode size, which means that the length of written extents may exceed the inode size, then fsck will fail. An example is given as:
dd if=/dev/urandom of=file bs=4M count=1 dax_iomap_rw iomap_iter // round 1 ext4_iomap_begin ext4_iomap_alloc // allocate 0~2M extents(written flag) dax_iomap_iter // copy 2M data iomap_iter // round 2 iomap_iter_advance iter->pos += iter->processed // iter->pos = 2M ext4_iomap_begin ext4_iomap_alloc // allocate 2~4M extents(written flag) dax_iomap_iter fatal_signal_pending done = iter->pos - iocb->ki_pos // done = 2M ext4_handle_inode_extension ext4_update_inode_size // inode size = 2M
fsck reports: Inode 13, i_size is 2097152, should be 4194304. Fix?
Fix the problem by truncating extents if the written length is smaller than expected.
Fixes: 776722e85d3b ("ext4: DAX iomap write support") CC: stable@vger.kernel.org Link: https://bugzilla.kernel.org/show_bug.cgi?id=219136 Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Zhihao Cheng chengzhihao1@huawei.com Link: https://patch.msgid.link/20240809121532.2105494-1-chengzhihao@huaweicloud.co... Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com --- fs/ext4/file.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 602349fc0bf0..ffa6bb50d23e 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -311,10 +311,10 @@ static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset, * Clean up the inode after DIO or DAX extending write has completed and the * inode size has been updated using ext4_handle_inode_extension(). */ -static void ext4_inode_extension_cleanup(struct inode *inode, ssize_t count) +static void ext4_inode_extension_cleanup(struct inode *inode, bool need_trunc) { lockdep_assert_held_write(&inode->i_rwsem); - if (count < 0) { + if (need_trunc) { ext4_truncate_failed_write(inode); /* * If the truncate operation failed early, then the inode may @@ -559,7 +559,7 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from) * writeback of delalloc blocks. */ WARN_ON_ONCE(ret == -EIOCBQUEUED); - ext4_inode_extension_cleanup(inode, ret); + ext4_inode_extension_cleanup(inode, ret < 0); }
out: @@ -643,7 +643,7 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (extend) { ret = ext4_handle_inode_extension(inode, offset, ret); - ext4_inode_extension_cleanup(inode, ret); + ext4_inode_extension_cleanup(inode, ret < (ssize_t)count); } out: inode_unlock(inode);