[PATCH 5.17 0286/1126] f2fs: fix compressed file start atomic write may cause data corruption

Greg Kroah-Hartman
2022-04-05T08:37:00Z

From: Fengnan Chang <changfengnan@vivo.com>

[ Upstream commit 9b56adcf525522e9ffa52471260298d91fc1d395 ]

When compressed file has blocks, f2fs_ioc_start_atomic_write will succeed,
but compressed flag will be remained in inode. If write partial compreseed
cluster and commit atomic write will cause data corruption.

This is the reproduction process:
Step 1:
create a compressed file ,write 64K data , call fsync(), then the blocks
are write as compressed cluster.
Step2:
iotcl(F2FS_IOC_START_ATOMIC_WRITE) --- this should be fail, but not.
write page 0 and page 3.
iotcl(F2FS_IOC_COMMIT_ATOMIC_WRITE) -- page 0 and 3 write as normal file,
Step3:
drop cache.
read page 0-4 -- Since page 0 has a valid block address, read as
non-compressed cluster, page 1 and 2 will be filled with compressed data
or zero.

The root cause is, after commit 7eab7a696827 ("f2fs: compress: remove
unneeded read when rewrite whole cluster"), in step 2, f2fs_write_begin()
only set target page dirty, and in f2fs_commit_inmem_pages(), we will write
partial raw pages into compressed cluster, result in corrupting compressed
cluster layout.

Fixes: 4c8ff7095bef ("f2fs: support data compression")
Fixes: 7eab7a696827 ("f2fs: compress: remove unneeded read when rewrite whole cluster")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/data.c | 2 +-
fs/f2fs/file.c | 5 ++++-
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index e1ef925be60c..bdfa8bed10b2 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3357,7 +3357,7 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,

*fsdata = NULL;

- if (len == PAGE_SIZE)
+ if (len == PAGE_SIZE && !(f2fs_is_atomic_file(inode)))
goto repeat;

ret = f2fs_prepare_compress_overwrite(inode, pagep,
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 3c98ef6af97d..b110c3a7db6a 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2008,7 +2008,10 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)

inode_lock(inode);

- f2fs_disable_compressed_file(inode);
+ if (!f2fs_disable_compressed_file(inode)) {
+ ret = -EINVAL;
+ goto out;
+ }

if (f2fs_is_atomic_file(inode)) {
if (is_inode_flag_set(inode, FI_ATOMIC_REVOKE_REQUEST))
--
2.34.1