[syzbot] [ext4?] BUG: unable to handle kernel paging request in ext4_calculate_overhead

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 47d9bb711707 Add linux-next specific files for 20230821
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=124d6a4ba80000
kernel config: https://syzkaller.appspot.com/x/.config?x=20999f779fa96017
dashboard link: https://syzkaller.appspot.com/bug?extid=b3123e6d9842e526de39
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110f9c0fa80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10b8867fa80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ffbe03c733b7/disk-47d9bb71.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a61a31d6caf9/vmlinux-47d9bb71.xz
kernel image: https://storage.googleapis.com/syzbot-assets/37e6f882b2d9/bzImage-47d9bb71.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/bf27f1330349/mount_0.gz

The issue was bisected to:

commit 99d6c5d892bfff3be40f83ec34d91d562125afd4
Author: Zhang Yi <yi.z...@huawei.com>
Date: Fri Aug 11 06:36:10 2023 +0000

ext4: ext4_get_{dev}_journal return proper error value

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13a381cfa80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=106381cfa80000
console output: https://syzkaller.appspot.com/x/log.txt?x=17a381cfa80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b3123e...@syzkaller.appspotmail.com
Fixes: 99d6c5d892bf ("ext4: ext4_get_{dev}_journal return proper error value")

EXT4-fs (loop0): ext4_check_descriptors: Checksum for group 0 failed (394!=20869)
EXT4-fs error (device loop0): ext4_get_journal_inode:5719: comm syz-executor999: inode #33: comm syz-executor999: iget: illegal inode #
EXT4-fs (loop0): no journal found
BUG: unable to handle page fault for address: ffffffffffffffdb
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD c979067 P4D c979067 PUD c97b067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5041 Comm: syz-executor999 Not tainted 6.5.0-rc7-next-20230821-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
RIP: 0010:ext4_calculate_overhead+0xfd2/0x1380 fs/ext4/super.c:4182
Code: 7b 50 48 89 fa 48 c1 ea 03 44 0f b6 60 14 48 b8 00 00 00 00 00 fc ff df 80 3c 02 00 0f 85 72 03 00 00 44 89 e6 bf 3f 00 00 00 <48> 8b 6b 50 e8 95 20 43 ff 41 80 fc 3f 0f 87 cb 20 ef 07 e8 56 25
RSP: 0018:ffffc9000399fa00 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffffffffffff8b RCX: 0000000000000000
RDX: 1ffffffffffffffb RSI: 000000000000000a RDI: 000000000000003f
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: 000000000000000a
R13: ffff888020936000 R14: dffffc0000000000 R15: ffff8880242a4000
FS: 0000555555f06380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffdb CR3: 0000000074f9b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__ext4_fill_super fs/ext4/super.c:5391 [inline]
ext4_fill_super+0x85e3/0xade0 fs/ext4/super.c:5643
get_tree_bdev+0x390/0x630 fs/super.c:1351
vfs_get_tree+0x88/0x350 fs/super.c:1524
do_new_mount fs/namespace.c:3335 [inline]
path_mount+0x1492/0x1ed0 fs/namespace.c:3662
do_mount fs/namespace.c:3675 [inline]
__do_sys_mount fs/namespace.c:3884 [inline]
__se_sys_mount fs/namespace.c:3861 [inline]
__x64_sys_mount+0x293/0x310 fs/namespace.c:3861
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f73494babba
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffae0148e8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffae0148f0 RCX: 00007f73494babba
RDX: 00000000200000c0 RSI: 0000000020000040 RDI: 00007fffae0148f0
RBP: 0000000000000004 R08: 00007fffae014930 R09: 00007fffae014930
R10: 0000000001000403 R11: 0000000000000202 R12: 00007fffae014930
R13: 0000000000000003 R14: 0000000000080000 R15: 0000000000000001
</TASK>
Modules linked in:
CR2: ffffffffffffffdb
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_calculate_overhead+0xfd2/0x1380 fs/ext4/super.c:4182
Code: 7b 50 48 89 fa 48 c1 ea 03 44 0f b6 60 14 48 b8 00 00 00 00 00 fc ff df 80 3c 02 00 0f 85 72 03 00 00 44 89 e6 bf 3f 00 00 00 <48> 8b 6b 50 e8 95 20 43 ff 41 80 fc 3f 0f 87 cb 20 ef 07 e8 56 25
RSP: 0018:ffffc9000399fa00 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffffffffffff8b RCX: 0000000000000000
RDX: 1ffffffffffffffb RSI: 000000000000000a RDI: 000000000000003f
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: 000000000000000a
R13: ffff888020936000 R14: dffffc0000000000 R15: ffff8880242a4000
FS: 0000555555f06380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffdb CR3: 0000000074f9b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 7b 50 jnp 0x52
2: 48 89 fa mov %rdi,%rdx
5: 48 c1 ea 03 shr $0x3,%rdx
9: 44 0f b6 60 14 movzbl 0x14(%rax),%r12d
e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
15: fc ff df
18: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
1c: 0f 85 72 03 00 00 jne 0x394
22: 44 89 e6 mov %r12d,%esi
25: bf 3f 00 00 00 mov $0x3f,%edi
* 2a: 48 8b 6b 50 mov 0x50(%rbx),%rbp <-- trapping instruction
2e: e8 95 20 43 ff call 0xff4320c8
33: 41 80 fc 3f cmp $0x3f,%r12b
37: 0f 87 cb 20 ef 07 ja 0x7ef2108
3d: e8 .byte 0xe8
3e: 56 push %rsi
3f: 25 .byte 0x25


---
This report is generated by a bot. It may contain errors.
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syzbot engineers can be reached at syzk...@googlegroups.com.

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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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#syz dup: exact-subject-of-another-report

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#syz undup

[Zhang Yi]

Thanks for the report, It's a real issue and I'm sorry to introduce
it due to my carelessness on commit '99d6c5d892bf ("ext4:
ext4_get_{dev}_journal return proper error value")'. The problem is
that I forgot to modify ext4_calculate_overhead() together to handle
the error return value from ext4_get_journal_inode() properly. I will
fix it soon.

Thanks,
Yi.

> .
>

[Edward AD]

From: Edward Adam Davis <ead...@sina.com>

please test invlaid j_inode return by ext4_get_journal_inode

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 47d9bb711707

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 34f5406c08da..0dac00954d25 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4178,7 +4178,7 @@ int ext4_calculate_overhead(struct super_block *sb)
else if (ext4_has_feature_journal(sb) && !sbi->s_journal && j_inum) {
/* j_inum for internal journal is non-zero */
j_inode = ext4_get_journal_inode(sb, j_inum);
- if (j_inode) {
+ if (j_inode && !IS_ERR(j_inode)) {
j_blocks = j_inode->i_size >> sb->s_blocksize_bits;
overhead += EXT4_NUM_B2C(sbi, j_blocks);
iput(j_inode);

[Edward AD]

In ext4_calculate_overhead(), ext4_get_journal_inode() returned an invalid inode
pointer without processing. Here, an invalid pointer judgment condition is added
to avoid incorrect operation of invalid pointer j_inode.

Reported-by: syzbot+b3123e...@syzkaller.appspotmail.com
Fixes: 99d6c5d892bf ("ext4: ext4_get_{dev}_journal return proper error value")

Signed-off-by: Edward AD <ead...@sina.com>
---
fs/ext4/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 34f5406c08da..0dac00954d25 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4178,7 +4178,7 @@ int ext4_calculate_overhead(struct super_block *sb)
else if (ext4_has_feature_journal(sb) && !sbi->s_journal && j_inum) {
/* j_inum for internal journal is non-zero */
j_inode = ext4_get_journal_inode(sb, j_inum);
- if (j_inode) {
+ if (j_inode && !IS_ERR(j_inode)) {
j_blocks = j_inode->i_size >> sb->s_blocksize_bits;
overhead += EXT4_NUM_B2C(sbi, j_blocks);
iput(j_inode);

--
2.25.1

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b3123e...@syzkaller.appspotmail.com

Tested on:

commit: 47d9bb71 Add linux-next specific files for 20230821
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=153e371fa80000

kernel config: https://syzkaller.appspot.com/x/.config?x=20999f779fa96017
dashboard link: https://syzkaller.appspot.com/bug?extid=b3123e6d9842e526de39
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1769307ba80000

Note: testing is done by a robot and is best-effort only.

[Jan Kara]

On Sat 26-08-23 11:55:54, Edward AD wrote:
> In ext4_calculate_overhead(), ext4_get_journal_inode() returned an invalid inode
> pointer without processing. Here, an invalid pointer judgment condition is added
> to avoid incorrect operation of invalid pointer j_inode.
>
> Reported-by: syzbot+b3123e...@syzkaller.appspotmail.com
> Fixes: 99d6c5d892bf ("ext4: ext4_get_{dev}_journal return proper error value")
> Signed-off-by: Edward AD <ead...@sina.com>

Thanks for the fixup but Ted has already merged the fixup from Zhang Yi [1].

Honza

[1] https://lore.kernel.org/all/20230826011029.2...@huaweicloud.com

> ---
> fs/ext4/super.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 34f5406c08da..0dac00954d25 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4178,7 +4178,7 @@ int ext4_calculate_overhead(struct super_block *sb)
> else if (ext4_has_feature_journal(sb) && !sbi->s_journal && j_inum) {
> /* j_inum for internal journal is non-zero */
> j_inode = ext4_get_journal_inode(sb, j_inum);
> - if (j_inode) {
> + if (j_inode && !IS_ERR(j_inode)) {
> j_blocks = j_inode->i_size >> sb->s_blocksize_bits;
> overhead += EXT4_NUM_B2C(sbi, j_blocks);
> iput(j_inode);
> --
> 2.25.1
>

--
Jan Kara <ja...@suse.com>
SUSE Labs, CR