6.17-stable review patch. If anyone has any objections, please let me know.
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From: Chao Yu chao@kernel.org
[ Upstream commit 930a9a6ee8e7ffa20af4bffbfc2bbd21d83bf81c ]
syzbot reported a f2fs bug as below:
Oops: gen[ 107.736417][ T5848] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 1 UID: 0 PID: 5848 Comm: syz-executor263 Tainted: G W 6.17.0-rc1-syzkaller-00014-g0e39a731820a #0 PREEMPT_{RT,(full)} RIP: 0010:strcmp+0x3c/0xc0 lib/string.c:284 Call Trace: <TASK> f2fs_check_quota_consistency fs/f2fs/super.c:1188 [inline] f2fs_check_opt_consistency+0x1378/0x2c10 fs/f2fs/super.c:1436 __f2fs_remount fs/f2fs/super.c:2653 [inline] f2fs_reconfigure+0x482/0x1770 fs/f2fs/super.c:5297 reconfigure_super+0x224/0x890 fs/super.c:1077 do_remount fs/namespace.c:3314 [inline] path_mount+0xd18/0xfe0 fs/namespace.c:4112 do_mount fs/namespace.c:4133 [inline] __do_sys_mount fs/namespace.c:4344 [inline] __se_sys_mount+0x317/0x410 fs/namespace.c:4321 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
The direct reason is f2fs_check_quota_consistency() may suffer null-ptr-deref issue in strcmp().
The bug can be reproduced w/ below scripts: mkfs.f2fs -f /dev/vdb mount -t f2fs -o usrquota /dev/vdb /mnt/f2fs quotacheck -uc /mnt/f2fs/ umount /mnt/f2fs mount -t f2fs -o usrjquota=aquota.user,jqfmt=vfsold /dev/vdb /mnt/f2fs mount -t f2fs -o remount,usrjquota=,jqfmt=vfsold /dev/vdb /mnt/f2fs umount /mnt/f2fs
So, before old_qname and new_qname comparison, we need to check whether they are all valid pointers, fix it.
Reported-by: syzbot+d371efea57d5aeab877b@syzkaller.appspotmail.com Fixes: d18535132523 ("f2fs: separate the options parsing and options checking") Closes: https://lore.kernel.org/linux-f2fs-devel/689ff889.050a0220.e29e5.0037.GAE@go... Cc: Hongbo Li lihongbo22@huawei.com Signed-off-by: Chao Yu chao@kernel.org Reviewed-by: Hongbo Li lihongbo22@huawei.com Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/f2fs/super.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 9f2ae3ac6078e..bf0497187bdff 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -1189,7 +1189,8 @@ static int f2fs_check_quota_consistency(struct fs_context *fc, goto err_jquota_change;
if (old_qname) { - if (strcmp(old_qname, new_qname) == 0) { + if (new_qname && + strcmp(old_qname, new_qname) == 0) { ctx->qname_mask &= ~(1 << i); continue; }