CVE-2025-38203: jfs: Fix null-ptr-deref in jfs_ioc_trim
In the Linux kernel, the following vulnerability has been resolved:
jfs: Fix null-ptr-deref in jfsioctrim
[ 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 Schedext: serialise (enabled+all), task: runnableat=-30ms RIP: 0010:jfsioctrim+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> ? diebody+0x61/0xb0 ? dieaddr+0xb1/0xe0 ? excgeneralprotection+0x333/0x510 ? asmexcgeneralprotection+0x26/0x30 ? jfsioctrim+0x34b/0x8f0 jfsioctl+0x3c8/0x4f0 ? pfxjfsioctl+0x10/0x10 ? pfxjfsioctl+0x10/0x10 sesysioctl+0x269/0x350 ? pfxsesysioctl+0x10/0x10 ? dosyscall64+0xfb/0x210 dosyscall64+0xee/0x210 ? syscallexittousermode+0x1e0/0x330 entrySYSCALL64afterhwframe+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 ORIGRAX: 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:jfsioctrim+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 JFSSBI(ipbmap->isb)->bmap is set to NULL in dbFreeBits and then dereferenced in jfsioctrim. This bug manifests quite rarely under normal circumstances, but is triggereable from a syz-program.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Patch d6c1b3599b2feb5c7291f5ac3a36e5fa7cedb234 - Compensating control
If practical while patching, mitigate the attack surface by restricting/monitoring access to the JFS ioctl entry point (jfs_ioctl/jfs_ioc_trim via the ioctl syscall) so untrusted processes cannot reliably trigger the null-ptr-deref under concurrency.
Event History
Frequently Asked Questions
What is the severity of CVE-2025-38203?
CVE-2025-38203 is classified as a moderate severity vulnerability affecting the Linux kernel.
How do I fix CVE-2025-38203?
To fix CVE-2025-38203, update to the patched version of the Linux kernel provided by your distribution.
What components are affected by CVE-2025-38203?
CVE-2025-38203 affects the jfs component of the Linux kernel.
What impact does CVE-2025-38203 have on system security?
CVE-2025-38203 can lead to a general protection fault, potentially allowing for a denial of service condition.
Is CVE-2025-38203 present in all versions of the Linux kernel?
No, CVE-2025-38203 is not present in all versions; it has been addressed in specific updates of the Linux kernel.