CVE-2025-38203

In the Linux kernel, the following vulnerability has been resolved:

jfs: Fix null-ptr-deref in jfs_ioc_trim

[ Syzkaller Report ]

Oops: general protection fault, probably for non-canonical address

0xdffffc0000000087: 0000 [#1

KASAN: null-ptr-deref in range [0x0000000000000438-0x000000000000043f]

CPU: 2 UID: 0 PID: 10614 Comm: syz-executor.0 Not tainted

6.13.0-rc6-gfbfd64d25c7a-dirty #1

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014

Sched_ext: serialise (enabled+all), task: runnable_at=-30ms

RIP: 0010:jfs_ioc_trim+0x34b/0x8f0

Code: e7 e8 59 a4 87 fe 4d 8b 24 24 4d 8d bc 24 38 04 00 00 48 8d 93

90 82 fe ff 4c 89 ff 31 f6

RSP: 0018:ffffc900055f7cd0 EFLAGS: 00010206

RAX: 0000000000000087 RBX: 00005866a9e67ff8 RCX: 000000000000000a

RDX: 0000000000000001 RSI: 0000000000000004 RDI: 0000000000000001

RBP: dffffc0000000000 R08: ffff88807c180003 R09: 1ffff1100f830000

R10: dffffc0000000000 R11: ffffed100f830001 R12: 0000000000000000

R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000438

FS: 00007fe520225640(0000) GS:ffff8880b7e80000(0000) knlGS:0000000000000000

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

CR2: 00005593c91b2c88 CR3: 000000014927c000 CR4: 00000000000006f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:

<TASK>

? __die_body+0x61/0xb0

? die_addr+0xb1/0xe0

? exc_general_protection+0x333/0x510

? asm_exc_general_protection+0x26/0x30

? jfs_ioc_trim+0x34b/0x8f0

jfs_ioctl+0x3c8/0x4f0

? __pfx_jfs_ioctl+0x10/0x10

? __pfx_jfs_ioctl+0x10/0x10

__se_sys_ioctl+0x269/0x350

? __pfx___se_sys_ioctl+0x10/0x10

? do_syscall_64+0xfb/0x210

do_syscall_64+0xee/0x210

? syscall_exit_to_user_mode+0x1e0/0x330

entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7fe51f4903ad

Code: c3 e8 a7 2b 00 00 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 89 f8 48

89 f7 48 89 d6 48 89 ca 4d

RSP: 002b:00007fe5202250c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010

RAX: ffffffffffffffda RBX: 00007fe51f5cbf80 RCX: 00007fe51f4903ad

RDX: 0000000020000680 RSI: 00000000c0185879 RDI: 0000000000000005

RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe520225640

R13: 000000000000000e R14: 00007fe51f44fca0 R15: 00007fe52021d000

</TASK>

Modules linked in:

---[ end trace 0000000000000000 ]---

RIP: 0010:jfs_ioc_trim+0x34b/0x8f0

Code: e7 e8 59 a4 87 fe 4d 8b 24 24 4d 8d bc 24 38 04 00 00 48 8d 93

90 82 fe ff 4c 89 ff 31 f6

RSP: 0018:ffffc900055f7cd0 EFLAGS: 00010206

RAX: 0000000000000087 RBX: 00005866a9e67ff8 RCX: 000000000000000a

RDX: 0000000000000001 RSI: 0000000000000004 RDI: 0000000000000001

RBP: dffffc0000000000 R08: ffff88807c180003 R09: 1ffff1100f830000

R10: dffffc0000000000 R11: ffffed100f830001 R12: 0000000000000000

R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000438

FS: 00007fe520225640(0000) GS:ffff8880b7e80000(0000) knlGS:0000000000000000

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

CR2: 00005593c91b2c88 CR3: 000000014927c000 CR4: 00000000000006f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Kernel panic - not syncing: Fatal exception

[ Analysis ]

We believe that we have found a concurrency bug in the `fs/jfs` module

that results in a null pointer dereference. There is a closely related

issue which has been fixed:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d6c1b3599b2feb5c7291f5ac3a36e5fa7cedb234

... but, unfortunately, the accepted patch appears to still be

susceptible to a null pointer dereference under some interleavings.

To trigger the bug, we think that `JFS_SBI(ipbmap->i_sb)->bmap` is set

to NULL in `dbFreeBits` and then dereferenced in `jfs_ioc_trim`. This

bug manifests quite rarely under normal circumstances, but is

triggereable from a syz-program.