[PATCH AUTOSEL 5.6 099/129] f2fs: fix NULL pointer dereference in f2fs_write_begin()

Sasha Levin
2020-04-15T13:00:35Z

From: Chao Yu <yuchao0@huawei.com>

[ Upstream commit 62f63eea291b50a5677ae7503ac128803174698a ]

BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:f2fs_write_begin+0x823/0xb90 [f2fs]
Call Trace:
f2fs_quota_write+0x139/0x1d0 [f2fs]
write_blk+0x36/0x80 [quota_tree]
get_free_dqblk+0x42/0xa0 [quota_tree]
do_insert_tree+0x235/0x4a0 [quota_tree]
do_insert_tree+0x26e/0x4a0 [quota_tree]
do_insert_tree+0x26e/0x4a0 [quota_tree]
do_insert_tree+0x26e/0x4a0 [quota_tree]
qtree_write_dquot+0x70/0x190 [quota_tree]
v2_write_dquot+0x43/0x90 [quota_v2]
dquot_acquire+0x77/0x100
f2fs_dquot_acquire+0x2f/0x60 [f2fs]
dqget+0x310/0x450
dquot_transfer+0x7e/0x120
f2fs_setattr+0x11a/0x4a0 [f2fs]
notify_change+0x349/0x480
chown_common+0x168/0x1c0
do_fchownat+0xbc/0xf0
__x64_sys_fchownat+0x20/0x30
do_syscall_64+0x5f/0x220
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Passing fsdata parameter to .write_{begin,end} in f2fs_quota_write(),
so that if quota file is compressed one, we can avoid above NULL
pointer dereference when updating quota content.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/super.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 3669f060b6257..8deb0a260d928 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1929,6 +1929,7 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
int offset = off & (sb->s_blocksize - 1);
size_t towrite = len;
struct page *page;
+ void *fsdata = NULL;
char *kaddr;
int err = 0;
int tocopy;
@@ -1938,7 +1939,7 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
towrite);
retry:
err = a_ops->write_begin(NULL, mapping, off, tocopy, 0,
- &page, NULL);
+ &page, &fsdata);
if (unlikely(err)) {
if (err == -ENOMEM) {
congestion_wait(BLK_RW_ASYNC, HZ/50);
@@ -1954,7 +1955,7 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
flush_dcache_page(page);

a_ops->write_end(NULL, mapping, off, tocopy, tocopy,
- page, NULL);
+ page, fsdata);
offset = 0;
towrite -= tocopy;
off += tocopy;
--
2.20.1