In the Linux kernel, the following vulnerability has been resolved:
riscv: Flush current cpu icache before other cpus
On SiFive Unmatched, I recently fell onto the following BUG when booting:
[ 0.000000] ftrace: allocating 36610 entries in 144 pages [ 0.000000] Oops - illegal instruction [#1] [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5 [ 0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT) [ 0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae [ 0.000000] ra : __sbi_rfence_v02+0xc8/0x10a [ 0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10 [ 0.000000] gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000 [ 0.000000] t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60 [ 0.000000] s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10 [ 0.000000] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 0.000000] a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43 [ 0.000000] s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000 [ 0.000000] s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001 [ 0.000000] s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000 [ 0.000000] s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008 [ 0.000000] t5 : ffffffcf04000808 t6 : ffffffe3ffddf188 [ 0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002 [ 0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae [ 0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26 [ 0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a [ 0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32 [ 0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c [ 0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360 [ 0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130 [ 0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6 [ 0.000000] ---[ end trace f67eb9af4d8d492b ]--- [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
While ftrace is looping over a list of addresses to patch, it always failed when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the backtrace, the illegal instruction is encountered in this same function. However, patch_text_nosync, after patching the instructions, calls flush_icache_range. But looking at what happens in this function:
flush_icache_range -> flush_icache_all -> sbi_remote_fence_i -> __sbi_rfence_v02 -> riscv_cpuid_to_hartid_mask
The icache and dcache of the current cpu are never synchronized between the patching of riscv_cpuid_to_hartid_mask and calling this same function.
So fix this by flushing the current cpu's icache before asking for the other cpus to do the same.
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Debian | — | Upgrade linux | Jul 30, 2024 | May 21, 2024 |
| Suse | — | Upgrade kernel-rt_debug-develUpgrade kernel-source-azureUpgrade kernel-kvmsmall-develUpgrade kernel-source-vanillaUpgrade kernel-rt-livepatchUpgrade dtb-appleUpgrade kernel-kvmsmall-livepatch-develUpgrade ocfs2-kmp-64kbUpgrade kernel-devel-azureUpgrade kernel-sourceUpgrade kselftests-kmp-64kbUpgrade dtb-sprdUpgrade kernel-default-livepatchUpgrade dtb-amdUpgrade kernel-64kb-optionalUpgrade kernel-64kb-extraUpgrade cluster-md-kmp-azureUpgrade dtb-amazonUpgrade ocfs2-kmp-azureUpgrade kernel-kvmsmall-vdsoUpgrade kernel-debug-develUpgrade kernel-default-develUpgrade kernel-default-optionalUpgrade kernel-rt-optionalUpgrade kernel-docs-htmlUpgrade dtb-broadcomUpgrade kernel-rt-vdsoUpgrade kernel-debug-vdsoUpgrade gfs2-kmp-defaultUpgrade kernel-source-rtUpgrade dtb-qcomUpgrade kernel-rt-extraUpgrade cluster-md-kmp-64kbUpgrade kernel-default-vdsoUpgrade dlm-kmp-64kbUpgrade reiserfs-kmp-64kbUpgrade dtb-lgUpgrade cluster-md-kmp-rtUpgrade dtb-exynosUpgrade kernel-rt_debug-livepatch-develUpgrade kernel-64kbUpgrade kselftests-kmp-azureUpgrade kernel-syms-azureUpgrade reiserfs-kmp-defaultUpgrade kernel-rtUpgrade gfs2-kmp-azureUpgrade dtb-caviumUpgrade kernel-azure-extraUpgrade kernel-develUpgrade kernel-azure-optionalUpgrade dtb-allwinnerUpgrade dtb-freescaleUpgrade kernel-obs-buildUpgrade dtb-alteraUpgrade dtb-marvellUpgrade ocfs2-kmp-defaultUpgrade kernel-azureUpgrade kernel-macrosUpgrade kernel-rt-develUpgrade kernel-docsUpgrade kselftests-kmp-rtUpgrade dtb-rockchipUpgrade cluster-md-kmp-defaultUpgrade kernel-default-base-rebuildUpgrade kernel-rt_debug-vdsoUpgrade gfs2-kmp-64kbUpgrade kernel-azure-vdsoUpgrade reiserfs-kmp-azureUpgrade reiserfs-kmp-rtUpgrade dtb-apmUpgrade kernel-64kb-develUpgrade dtb-hisiliconUpgrade kernel-debugUpgrade kernel-kvmsmallUpgrade kernel-rt-livepatch-develUpgrade dtb-armUpgrade dtb-renesasUpgrade kernel-rt_debugUpgrade kernel-debug-livepatch-develUpgrade kernel-default-extraUpgrade kernel-syms-rtUpgrade kernel-default-livepatch-develUpgrade kselftests-kmp-defaultUpgrade kernel-devel-rtUpgrade dtb-xilinxUpgrade kernel-defaultUpgrade kernel-zfcpdumpUpgrade dlm-kmp-azureUpgrade dtb-nvidiaUpgrade dlm-kmp-rtUpgrade kernel-azure-develUpgrade gfs2-kmp-rtUpgrade kernel-obs-qaUpgrade dlm-kmp-defaultUpgrade kernel-symsUpgrade dtb-mediatekUpgrade ocfs2-kmp-rtUpgrade kernel-azure-livepatch-develUpgrade kernel-64kb-livepatch-develUpgrade dtb-amlogicUpgrade kernel-default-baseUpgrade dtb-socionext | Aug 9, 2024 | May 21, 2024 |
| Ubuntu | — | No solution exists | Jun 26, 2025 | May 21, 2024 |
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