5.4-stable review patch. If anyone has any objections, please let me know.
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From: Jan Kara jack@suse.cz
[ Upstream commit 65121eff3e4c8c90f8126debf3c369228691c591 ]
If the extended attribute size is not a multiple of block size, the last block in the EA inode will have uninitialized tail which will get written to disk. We will never expose the data to userspace but still this is not a good practice so just zero out the tail of the block as it isn't going to cause a noticeable performance overhead.
Fixes: e50e5129f384 ("ext4: xattr-in-inode support") Reported-by: syzbot+9c1fe13fcb51574b249b@syzkaller.appspotmail.com Reported-by: Hugh Dickins hughd@google.com Signed-off-by: Jan Kara jack@suse.cz Link: https://patch.msgid.link/20240613150234.25176-1-jack@suse.cz Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/xattr.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index cb7faaa935cc6..d65f1eb85a924 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -1396,6 +1396,12 @@ static int ext4_xattr_inode_write(handle_t *handle, struct inode *ea_inode, goto out;
memcpy(bh->b_data, buf, csize); + /* + * Zero out block tail to avoid writing uninitialized memory + * to disk. + */ + if (csize < blocksize) + memset(bh->b_data + csize, 0, blocksize - csize); set_buffer_uptodate(bh); ext4_handle_dirty_metadata(handle, ea_inode, bh);