We use these services and cookies to improve your user experience. You may opt out if you wish, however, this may limit some features on this site.
Please see our statement on Data Privacy.
Assigner | Linux |
Reserved | 2024-09-30 |
Published | 2024-10-21 |
Updated | 2024-11-05 |
In the Linux kernel, the following vulnerability has been resolved: ARM: 9410/1: vfp: Use asm volatile in fmrx/fmxr macros Floating point instructions in userspace can crash some arm kernels built with clang/LLD 17.0.6: BUG: unsupported FP instruction in kernel mode FPEXC == 0xc0000780 Internal error: Oops - undefined instruction: 0 [#1] ARM CPU: 0 PID: 196 Comm: vfp-reproducer Not tainted 6.10.0 #1 Hardware name: BCM2835 PC is at vfp_support_entry+0xc8/0x2cc LR is at do_undefinstr+0xa8/0x250 pc : [<c0101d50>] lr : [<c010a80c>] psr: a0000013 sp : dc8d1f68 ip : 60000013 fp : bedea19c r10: ec532b17 r9 : 00000010 r8 : 0044766c r7 : c0000780 r6 : ec532b17 r5 : c1c13800 r4 : dc8d1fb0 r3 : c10072c4 r2 : c0101c88 r1 : ec532b17 r0 : 0044766c Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 00c5387d Table: 0251c008 DAC: 00000051 Register r0 information: non-paged memory Register r1 information: vmalloc memory Register r2 information: non-slab/vmalloc memory Register r3 information: non-slab/vmalloc memory Register r4 information: 2-page vmalloc region Register r5 information: slab kmalloc-cg-2k Register r6 information: vmalloc memory Register r7 information: non-slab/vmalloc memory Register r8 information: non-paged memory Register r9 information: zero-size pointer Register r10 information: vmalloc memory Register r11 information: non-paged memory Register r12 information: non-paged memory Process vfp-reproducer (pid: 196, stack limit = 0x61aaaf8b) Stack: (0xdc8d1f68 to 0xdc8d2000) 1f60: 0000081f b6f69300 0000000f c10073f4 c10072c4 dc8d1fb0 1f80: ec532b17 0c532b17 0044766c b6f9ccd8 00000000 c010a80c 00447670 60000010 1fa0: ffffffff c1c13800 00c5387d c0100f10 b6f68af8 00448fc0 00000000 bedea188 1fc0: bedea314 00000001 00448ebc b6f9d000 00447608 b6f9ccd8 00000000 bedea19c 1fe0: bede9198 bedea188 b6e1061c 0044766c 60000010 ffffffff 00000000 00000000 Call trace: [<c0101d50>] (vfp_support_entry) from [<c010a80c>] (do_undefinstr+0xa8/0x250) [<c010a80c>] (do_undefinstr) from [<c0100f10>] (__und_usr+0x70/0x80) Exception stack(0xdc8d1fb0 to 0xdc8d1ff8) 1fa0: b6f68af8 00448fc0 00000000 bedea188 1fc0: bedea314 00000001 00448ebc b6f9d000 00447608 b6f9ccd8 00000000 bedea19c 1fe0: bede9198 bedea188 b6e1061c 0044766c 60000010 ffffffff Code: 0a000061 e3877202 e594003c e3a09010 (eef16a10) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Fatal exception in interrupt ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]--- This is a minimal userspace reproducer on a Raspberry Pi Zero W: #include <stdio.h> #include <math.h> int main(void) { double v = 1.0; printf("%fn", NAN + *(volatile double *)&v); return 0; } Another way to consistently trigger the oops is: calvin@raspberry-pi-zero-w ~$ python -c "import json" The bug reproduces only when the kernel is built with DYNAMIC_DEBUG=n, because the pr_debug() calls act as barriers even when not activated. This is the output from the same kernel source built with the same compiler and DYNAMIC_DEBUG=y, where the userspace reproducer works as expected: VFP: bounce: trigger ec532b17 fpexc c0000780 VFP: emulate: INST=0xee377b06 SCR=0x00000000 VFP: bounce: trigger eef1fa10 fpexc c0000780 VFP: emulate: INST=0xeeb40b40 SCR=0x00000000 VFP: raising exceptions 30000000 calvin@raspberry-pi-zero-w ~$ ./vfp-reproducer nan Crudely grepping for vmsr/vmrs instructions in the otherwise nearly idential text for vfp_support_entry() makes the problem obvious: vmlinux.llvm.good [0xc0101cb8] <+48>: vmrs r7, fpexc vmlinux.llvm.good [0xc0101cd8] <+80>: vmsr fpexc, r0 vmlinux.llvm.good [0xc0101d20 ---truncated---
https://git.kernel.org/stable/c/9fc60f2bdd43e758bdf0305c0fc83221419ddb3f
https://git.kernel.org/stable/c/cd595d87e5fdd2fc09ea69359aa85e7f12f4b97b
https://git.kernel.org/stable/c/39caf610a63786b3b0ef3348ac015edc19827d6a
https://git.kernel.org/stable/c/89a906dfa8c3b21b3e5360f73c49234ac1eb885b