UBUNTU-CVE-2025-68367: Race Condition
In the Linux kernel, the following vulnerability has been resolved: macintosh/machid: fix race condition in machidtoggleemumouse The following warning appears when running syzkaller, and this issue also exists in the mainline code. ------------[ cut here ]------------ listadd double add: new=ffffffffa57eee28, prev=ffffffffa57eee28, next=ffffffffa5e63100. WARNING: CPU: 0 PID: 1491 at lib/listdebug.c:35 listaddvalidorreport+0xf7/0x130 Modules linked in: CPU: 0 PID: 1491 Comm: syz.1.28 Not tainted 6.6.0+ #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:listaddvalidorreport+0xf7/0x130 RSP: 0018:ff1100010dfb7b78 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffffffffa57eee18 RCX: ffffffff97fc9817 RDX: 0000000000040000 RSI: ffa0000002383000 RDI: 0000000000000001 RBP: ffffffffa57eee28 R08: 0000000000000001 R09: ffe21c0021bf6f2c R10: 0000000000000001 R11: 6464615f7473696c R12: ffffffffa5e63100 R13: ffffffffa57eee28 R14: ffffffffa57eee28 R15: ff1100010dfb7d48 FS: 00007fb14398b640(0000) GS:ff11000119600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000010d096005 CR4: 0000000000773ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 80000000 Call Trace: <TASK> inputregisterhandler+0xb3/0x210 machidstartemulation+0x1c5/0x290 machidtoggleemumouse+0x20a/0x240 procsyscallhandler+0x4c2/0x6e0 newsyncwrite+0x1b1/0x2d0 vfswrite+0x709/0x950 ksyswrite+0x12a/0x250 dosyscall64+0x5a/0x110 entrySYSCALL64afterhwframe+0x78/0xe2 The WARNING occurs when two processes concurrently write to the mac-hid emulation sysctl, causing a race condition in machidtoggleemumouse(). Both processes read oldval=0, then both try to register the input handler, leading to a double listadd of the same handler. CPU0 CPU1 ------------------------- ------------------------- vfswrite() //write 1 vfswrite() //write 1 procsyswrite() procsyswrite() machidtoggleemumouse() machidtoggleemumouse() oldval = valp // oldval=0 oldval = valp // oldval=0 mutexlockkillable() procdointvec() // valp=1 machidstartemulation() inputregisterhandler() mutexunlock() mutexlockkillable() procdointvec() machidstartemulation() inputregisterhandler() //Trigger Warning mutexunlock() Fix this by moving the oldval read inside the mutex lock region.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-110.110+fips2 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1054.57+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.17.0-19.19 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.17.0-1009.9 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.17.0-1010.10 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.17.0-1009.9 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.17.0-1008.9 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 6.17.0-19.19.1 - Compensating control
Fix mac_hid_toggle_emumouse() by moving the old_val read inside the mutex lock region, so concurrent writes cannot both observe the old value and register the same input handler.
Event History
Frequently Asked Questions
Which Ubuntu kernel packages are listed as affected?
The issue is listed for ubuntu/linux, ubuntu/linux-fips, ubuntu/linux-aws, ubuntu/linux-azure, ubuntu/linux-aws-fips, ubuntu/linux-azure-fips, ubuntu/linux-gcp, and ubuntu/linux-gcp-fips.
What evidence may indicate that the race condition has occurred?
The reported symptom is a kernel warning for a list double-add, originating in __list_add_valid_or_report. The warning was observed during syzkaller testing and is stated to also exist in mainline code.