[PATCH 5.8 407/633] f2fs: reject CASEFOLD inode flag without casefold feature

Greg Kroah-Hartman
2020-10-27T17:07:37Z

From: Eric Biggers <ebiggers@google.com>

[ Upstream commit f6322f3f1212e005e7e6aa82ceb62be53030a64b ]

syzbot reported:

general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 6860 Comm: syz-executor835 Not tainted 5.9.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:utf8_casefold+0x43/0x1b0 fs/unicode/utf8-core.c:107
[...]
Call Trace:
f2fs_init_casefolded_name fs/f2fs/dir.c:85 [inline]
__f2fs_setup_filename fs/f2fs/dir.c:118 [inline]
f2fs_prepare_lookup+0x3bf/0x640 fs/f2fs/dir.c:163
f2fs_lookup+0x10d/0x920 fs/f2fs/namei.c:494
__lookup_hash+0x115/0x240 fs/namei.c:1445
filename_create+0x14b/0x630 fs/namei.c:3467
user_path_create fs/namei.c:3524 [inline]
do_mkdirat+0x56/0x310 fs/namei.c:3664
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]

The problem is that an inode has F2FS_CASEFOLD_FL set, but the
filesystem doesn't have the casefold feature flag set, and therefore
super_block::s_encoding is NULL.

Fix this by making sanity_check_inode() reject inodes that have
F2FS_CASEFOLD_FL when the filesystem doesn't have the casefold feature.

Reported-by: syzbot+05139c4039d0679e19ff@syzkaller.appspotmail.com
Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/inode.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 44582a4db513e..1e014535c2530 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -287,6 +287,13 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
return false;
}

+ if ((fi->i_flags & F2FS_CASEFOLD_FL) && !f2fs_sb_has_casefold(sbi)) {
+ set_sbi_flag(sbi, SBI_NEED_FSCK);
+ f2fs_warn(sbi, "%s: inode (ino=%lx) has casefold flag, but casefold feature is off",
+ __func__, inode->i_ino);
+ return false;
+ }
+
if (f2fs_has_extra_attr(inode) && f2fs_sb_has_compression(sbi) &&
fi->i_flags & F2FS_COMPR_FL &&
F2FS_FITS_IN_INODE(ri, fi->i_extra_isize,
--
2.25.1