[syzbot] [ext4?] general protection fault in utf8nlookup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e42bebf6db29 Merge tag 'efi-fixes-for-v6.6-1' of git://git..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=179f4a38680000
kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
dashboard link: https://syzkaller.appspot.com/bug?extid=9cf75dc581fb4307d6dd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1374a174680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12b12928680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/14a6a5d23944/disk-e42bebf6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/98cc4c220388/vmlinux-e42bebf6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6a1d09cf21bf/bzImage-e42bebf6.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/37e5beb24789/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/f219a9e665e9/mount_8.gz

The issue was bisected to:

commit b81427939590450172716093dafdda8ef52e020f
Author: Eric Biggers <ebig...@google.com>
Date: Mon Aug 14 18:29:02 2023 +0000

ext4: remove redundant checks of s_encoding

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10852352680000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12852352680000
console output: https://syzkaller.appspot.com/x/log.txt?x=14852352680000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9cf75d...@syzkaller.appspotmail.com
Fixes: b81427939590 ("ext4: remove redundant checks of s_encoding")

EXT4-fs error (device loop0): ext4_do_update_inode:5097: inode #2: comm syz-executor379: corrupted inode contents
EXT4-fs error (device loop0): __ext4_ext_dirty:202: inode #2: comm syz-executor379: mark_inode_dirty error
general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 1 PID: 5031 Comm: syz-executor379 Not tainted 6.6.0-rc1-syzkaller-00125-ge42bebf6db29 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
RIP: 0010:utf8nlookup+0x39/0xaa0 fs/unicode/utf8-norm.c:306
Code: 89 c4 48 89 4c 24 08 48 89 14 24 89 f5 49 89 fd 49 be 00 00 00 00 00 fc ff df e8 22 a5 ea fe 49 8d 5d 18 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 df e8 c8 93 44 ff 48 8b 1b 48 83 c3 30
RSP: 0018:ffffc90003e0f800 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff88801be79dc0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: ffffc90003e0f998 R11: fffff520007c1f36 R12: 0000000000000005
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff8880792de070
FS: 0000555556220480(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa9b1ff3870 CR3: 000000002a7f4000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
utf8byte+0x334/0x1350
utf8_casefold+0x125/0x220 fs/unicode/utf8-core.c:109
ext4_fname_setup_ci_filename+0x1b0/0x430 fs/ext4/namei.c:1458
ext4_fname_prepare_lookup+0x2f7/0x4e0 fs/ext4/crypto.c:55
ext4_lookup_entry fs/ext4/namei.c:1760 [inline]
ext4_lookup+0x121/0x750 fs/ext4/namei.c:1835
lookup_one_qstr_excl+0x11b/0x250 fs/namei.c:1608
filename_create+0x297/0x530 fs/namei.c:3890
do_mkdirat+0xb7/0x520 fs/namei.c:4135
__do_sys_mkdir fs/namei.c:4163 [inline]
__se_sys_mkdir fs/namei.c:4161 [inline]
__x64_sys_mkdir+0x6e/0x80 fs/namei.c:4161
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f4bdc54d557
Code: ff ff 77 07 31 c0 c3 0f 1f 40 00 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 b8 53 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:00007fffbf49c838 EFLAGS: 00000286 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007f4bdc54d557
RDX: 0000000000000040 RSI: 00000000000001ff RDI: 0000000020000540
RBP: 00007fffbf49c8d0 R08: 00000000000000fd R09: 0000000000000000
R10: 0000000000000249 R11: 0000000000000286 R12: 0000000020000540
R13: 00000000200000c0 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:utf8nlookup+0x39/0xaa0 fs/unicode/utf8-norm.c:306
Code: 89 c4 48 89 4c 24 08 48 89 14 24 89 f5 49 89 fd 49 be 00 00 00 00 00 fc ff df e8 22 a5 ea fe 49 8d 5d 18 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 df e8 c8 93 44 ff 48 8b 1b 48 83 c3 30
RSP: 0018:ffffc90003e0f800 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff88801be79dc0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: ffffc90003e0f998 R11: fffff520007c1f36 R12: 0000000000000005
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff8880792de070
FS: 0000555556220480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005650cf4460b8 CR3: 000000002a7f4000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 89 c4 mov %eax,%esp
2: 48 89 4c 24 08 mov %rcx,0x8(%rsp)
7: 48 89 14 24 mov %rdx,(%rsp)
b: 89 f5 mov %esi,%ebp
d: 49 89 fd mov %rdi,%r13
10: 49 be 00 00 00 00 00 movabs $0xdffffc0000000000,%r14
17: fc ff df
1a: e8 22 a5 ea fe call 0xfeeaa541
1f: 49 8d 5d 18 lea 0x18(%r13),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 30 00 cmpb $0x0,(%rax,%r14,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 df mov %rbx,%rdi
34: e8 c8 93 44 ff call 0xff449401
39: 48 8b 1b mov (%rbx),%rbx
3c: 48 83 c3 30 add $0x30,%rbx


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
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
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Eric Biggers]

This report is expected for now, since the repro involves writing to the page
cache of a mounted block device. For more information see
https://lore.kernel.org/linux-fsdevel/20230813001...@sol.localdomain and
https://lore.kernel.org/linux-fsdevel/20230814182903....@kernel.org.
Also https://lore.kernel.org/linux-fsdevel/2023070412272...@suse.cz
which will ultimately be the fix for this class of issue.

Note: the repro that syzkaller generated for this is very strange (even moreso
than usual for syzkaller repros...) because it replaces its "scratch space" at
address 0x20000000 with a different mapping, specifically a mapping for a file
that is mounted as a filesystem via loopback. That makes "syscalls" have weird
side effects as a result of the repro writing parameters to the address that is
supposed to contain its scratch space. I don't think this should be happening,
so I've opened https://github.com/google/syzkaller/issues/4216 for it.

- Eric

[Edward AD]

please test null ptr in utf8nlookup

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e42bebf6db29

diff --git a/fs/unicode/utf8-norm.c b/fs/unicode/utf8-norm.c
index 768f8ab448b8..0437eda38991 100644
--- a/fs/unicode/utf8-norm.c
+++ b/fs/unicode/utf8-norm.c
@@ -422,6 +422,10 @@ int utf8ncursor(struct utf8cursor *u8c, const struct unicode_map *um,
{
if (!s)
return -1;
+
+ if (IS_ERR(um))
+ return -1;
+
u8c->um = um;
u8c->n = n;
u8c->s = s;

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in utf8nlookup

EXT4-fs error (device loop0): ext4_do_update_inode:5097: inode #2: comm syz-executor.0: corrupted inode contents
EXT4-fs error (device loop0): ext4_dirty_inode:5956: inode #2: comm syz-executor.0: mark_inode_dirty error
EXT4-fs error (device loop0): ext4_do_update_inode:5097: inode #2: comm syz-executor.0: corrupted inode contents
EXT4-fs error (device loop0): __ext4_ext_dirty:202: inode #2: comm syz-executor.0: mark_inode_dirty error

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]

CPU: 1 PID: 5466 Comm: syz-executor.0 Not tainted 6.6.0-rc1-syzkaller-00125-ge42bebf6db29-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
RIP: 0010:utf8nlookup+0x39/0xaa0 fs/unicode/utf8-norm.c:306
Code: 89 c4 48 89 4c 24 08 48 89 14 24 89 f5 49 89 fd 49 be 00 00 00 00 00 fc ff df e8 22 a5 ea fe 49 8d 5d 18 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 df e8 c8 93 44 ff 48 8b 1b 48 83 c3 30

RSP: 0018:ffffc9000539f800 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888026cc8000

RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000

R10: ffffc9000539f998 R11: fffff52000a73f36 R12: 0000000000000005
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88806a74d210
FS: 00007f0eaa6896c0(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020000080 CR3: 000000006ad2f000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
utf8byte+0x334/0x1350
utf8_casefold+0x125/0x220 fs/unicode/utf8-core.c:109
ext4_fname_setup_ci_filename+0x1b0/0x430 fs/ext4/namei.c:1458
ext4_fname_prepare_lookup+0x2f7/0x4e0 fs/ext4/crypto.c:55
ext4_lookup_entry fs/ext4/namei.c:1760 [inline]
ext4_lookup+0x121/0x750 fs/ext4/namei.c:1835
lookup_one_qstr_excl+0x11b/0x250 fs/namei.c:1608
filename_create+0x297/0x530 fs/namei.c:3890
do_mkdirat+0xb7/0x520 fs/namei.c:4135

__do_sys_mkdirat fs/namei.c:4158 [inline]
__se_sys_mkdirat fs/namei.c:4156 [inline]
__x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4156

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

RIP: 0033:0x7f0ea987b5e7
Code: 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 02 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0eaa688ee8 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000020000300 RCX: 00007f0ea987b5e7
RDX: 00000000000001ff RSI: 0000000020000540 RDI: 00000000ffffff9c
RBP: 00000000200000c0 R08: 00000000000000fd R09: 0000000000000000
R10: 00000000200000c0 R11: 0000000000000246 R12: 0000000020000540
R13: 00007f0eaa688f40 R14: 0000000000000000 R15: 0000000000000000

</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:utf8nlookup+0x39/0xaa0 fs/unicode/utf8-norm.c:306
Code: 89 c4 48 89 4c 24 08 48 89 14 24 89 f5 49 89 fd 49 be 00 00 00 00 00 fc ff df e8 22 a5 ea fe 49 8d 5d 18 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 df e8 c8 93 44 ff 48 8b 1b 48 83 c3 30

RSP: 0018:ffffc9000539f800 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888026cc8000

RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000

R10: ffffc9000539f998 R11: fffff52000a73f36 R12: 0000000000000005
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88806a74d210
FS: 00007f0eaa6896c0(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020000080 CR3: 000000006ad2f000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

----------------
Code disassembly (best guess):
0: 89 c4 mov %eax,%esp
2: 48 89 4c 24 08 mov %rcx,0x8(%rsp)
7: 48 89 14 24 mov %rdx,(%rsp)
b: 89 f5 mov %esi,%ebp
d: 49 89 fd mov %rdi,%r13
10: 49 be 00 00 00 00 00 movabs $0xdffffc0000000000,%r14
17: fc ff df
1a: e8 22 a5 ea fe call 0xfeeaa541
1f: 49 8d 5d 18 lea 0x18(%r13),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 30 00 cmpb $0x0,(%rax,%r14,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 df mov %rbx,%rdi
34: e8 c8 93 44 ff call 0xff449401
39: 48 8b 1b mov (%rbx),%rbx
3c: 48 83 c3 30 add $0x30,%rbx

Tested on:

commit: e42bebf6 Merge tag 'efi-fixes-for-v6.6-1' of git://git..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=128650f2680000

kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
dashboard link: https://syzkaller.appspot.com/bug?extid=9cf75dc581fb4307d6dd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16cb9cd2680000

[Edward AD]

please test null ptr in utf8nlookup

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e42bebf6db29

diff --git a/fs/unicode/utf8-norm.c b/fs/unicode/utf8-norm.c
index 768f8ab448b8..0437eda38991 100644
--- a/fs/unicode/utf8-norm.c
+++ b/fs/unicode/utf8-norm.c
@@ -422,6 +422,10 @@ int utf8ncursor(struct utf8cursor *u8c, const struct unicode_map *um,
{
if (!s)
return -1;
+

+ if (IS_ERR_OR_NULL(um))

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+9cf75d...@syzkaller.appspotmail.com

Tested on:

commit: e42bebf6 Merge tag 'efi-fixes-for-v6.6-1' of git://git..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

console output: https://syzkaller.appspot.com/x/log.txt?x=103f2cf4680000

kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
dashboard link: https://syzkaller.appspot.com/bug?extid=9cf75dc581fb4307d6dd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16b11686680000

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

[Edward AD]

When init struct utf8cursor *u8c in utf8ncursor(), we need check um is
valid.

Reported-and-tested-by: syzbot+9cf75d...@syzkaller.appspotmail.com

Fixes: b81427939590 ("ext4: remove redundant checks of s_encoding")

Signed-off-by: Edward AD <twuu...@gmail.com>
---
fs/unicode/utf8-norm.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/unicode/utf8-norm.c b/fs/unicode/utf8-norm.c
index 768f8ab448b8..906b639b2f38 100644

--- a/fs/unicode/utf8-norm.c
+++ b/fs/unicode/utf8-norm.c
@@ -422,6 +422,10 @@ int utf8ncursor(struct utf8cursor *u8c, const struct unicode_map *um,
{
if (!s)
return -1;
+
+ if (IS_ERR_OR_NULL(um))
+ return -1;
+
u8c->um = um;
u8c->n = n;
u8c->s = s;

--
2.25.1

[Eric Biggers]

See https://lore.kernel.org/linux-fsdevel/2023092007...@sol.localdomain/

- Eric

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 6f861765464f43a71462d52026fbddfc858239a5
Author: Jan Kara <ja...@suse.cz>
Date: Wed Nov 1 17:43:10 2023 +0000

fs: Block writes to mounted block devices

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17547fd4180000
start commit: e42bebf6db29 Merge tag 'efi-fixes-for-v6.6-1' of git://git..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
dashboard link: https://syzkaller.appspot.com/bug?extid=9cf75dc581fb4307d6dd

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1374a174680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12b12928680000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: fs: Block writes to mounted block devices

[Jan Kara]

On Mon 12-02-24 16:24:03, syzbot wrote:
> syzbot suspects this issue was fixed by commit:
>
> commit 6f861765464f43a71462d52026fbddfc858239a5
> Author: Jan Kara <ja...@suse.cz>
> Date: Wed Nov 1 17:43:10 2023 +0000
>
> fs: Block writes to mounted block devices
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17547fd4180000
> start commit: e42bebf6db29 Merge tag 'efi-fixes-for-v6.6-1' of git://git..
> git tree: upstream
> kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
> dashboard link: https://syzkaller.appspot.com/bug?extid=9cf75dc581fb4307d6dd
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1374a174680000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12b12928680000
>
> If the result looks correct, please mark the issue as fixed by replying with:

The reproducer definitely does weird stuff like mmapping the loop device.
So makes sense:

#syz fix: fs: Block writes to mounted block devices

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