CVE-2024-50072

Summary

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. ]

Affected Software

VendorProductVersion RangeStatus
LinuxLinux50f021f0b985629accf10481a6e89af8b9700583 < bfd1d223d80cb29a210caa1bd5e21f0816d58f02affected
LinuxLinuxd54de9f2a127090f2017184e8257795b487d5312 < ada431c6c31a2c8c37991c46089af5caa23a9c6eaffected
LinuxLinux2e3087505ddb8ba2d3d4c81306cca11e868fcdb9 < 38c5fe74f3bef98f75d16effa49836d50c9b6097affected
LinuxLinuxca13d8cd8dac25558da4ee8df4dc70e8e7f9d762 < 481b477ab63c7245715a3e57ba79eb87c2dc0d02affected
LinuxLinuxa0e2dab44d22b913b4c228c8b52b2a104434b0b3 < bc576fbaf82deded606e69a00efe9752136bf91daffected
LinuxLinuxa0e2dab44d22b913b4c228c8b52b2a104434b0b3 < e4d2102018542e3ae5e297bc6e229303abff8a0faffected
LinuxLinux51eca9f1fd047b500137d021f882d93f03280118affected
LinuxLinux5.10.215 < 5.10.229affected
LinuxLinux5.15.154 < 5.15.171affected
LinuxLinux6.1.81 < 6.1.116affected
LinuxLinux6.6.21 < 6.6.58affected
LinuxLinux6.7.9 < 6.8affected
LinuxLinux6.8affected
LinuxLinux0 < 6.8unaffected
LinuxLinux5.10.229 <= 5.10.*unaffected
LinuxLinux5.15.171 <= 5.15.*unaffected
LinuxLinux6.1.116 <= 6.1.*unaffected
LinuxLinux6.6.58 <= 6.6.*unaffected
LinuxLinux6.11.5 <= 6.11.*unaffected
LinuxLinux6.12 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

References