linux-kernel - [PATCH 5.15 260/913] f2fs: fix compressed file start atomic write may cause data corruption

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Date:   Tue,  5 Apr 2022 09:22:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Fengnan Chang <changfengnan@...o.com>,
        Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 260/913] f2fs: fix compressed file start atomic write may cause data corruption

From: Fengnan Chang <changfengnan@...o.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@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Fengnan Chang <changfengnan@...o.com>
Reviewed-by: Chao Yu <chao@...nel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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 f6e9fc36b837..4cf522120cb1 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3410,7 +3410,7 @@ 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 7ed44752c758..0e14dc41ed4e 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2002,7 +2002,10 @@ 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