CVE-2024-50072

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: x86/bugs: Use code segment selector for VERW operand Robert Gill reported below #GP in 32-bit mode when dosemu software was executing vm86() system call: general protection fault: 0000 [#1] PREEMPT SMP CPU: 4 PID: 4610 Comm: dosemu.bin Not tainted 6.6.21-gentoo-x86 #1 Hardware name: Dell Inc. PowerEdge 1950/0H723K, BIOS 2.7.0 10/30/2010 EIP: restore_all_switch_stack+0xbe/0xcf EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000 ESI: 00000000 EDI: 00000000 EBP: 00000000 ESP: ff8affdc DS: 0000 ES: 0000 FS: 0000 GS: 0033 SS: 0068 EFLAGS: 00010046 CR0: 80050033 CR2: 00c2101c CR3: 04b6d000 CR4: 000406d0 Call Trace: show_regs+0x70/0x78 die_addr+0x29/0x70 exc_general_protection+0x13c/0x348 exc_bounds+0x98/0x98 handle_exception+0x14d/0x14d exc_bounds+0x98/0x98 restore_all_switch_stack+0xbe/0xcf exc_bounds+0x98/0x98 restore_all_switch_stack+0xbe/0xcf This only happens in 32-bit mode when VERW based mitigations like MDS/RFDS are enabled. This is because segment registers with an arbitrary user value can result in #GP when executing VERW. Intel SDM vol. 2C documents the following behavior for VERW instruction: #GP(0) - If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. CLEAR_CPU_BUFFERS macro executes VERW instruction before returning to user space. Use %cs selector to reference VERW operand. This ensures VERW will not #GP for an arbitrary user %ds. [ mingo: Fixed the SOB chain. ]

CVSS Score

Affected Products

References

• https://git.kernel.org/stable/c/38c5fe74f3bef98f75d16effa49836d50c9b6097
• https://git.kernel.org/stable/c/481b477ab63c7245715a3e57ba79eb87c2dc0d02Patch
• https://git.kernel.org/stable/c/ada431c6c31a2c8c37991c46089af5caa23a9c6e
• https://git.kernel.org/stable/c/bc576fbaf82deded606e69a00efe9752136bf91dPatch
• https://git.kernel.org/stable/c/bfd1d223d80cb29a210caa1bd5e21f0816d58f02
• https://git.kernel.org/stable/c/e4d2102018542e3ae5e297bc6e229303abff8a0fPatch
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html