| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47414: riscv: Flush current cpu icache before other cpus |
| |
| Description |
| =========== |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47414 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.15 with commit fab957c11efe2f405e08b9f0d080524bc2631428 and fixed in 5.10.73 with commit 427faa29e06f0709476ea1bd59758f997ec8b64e |
| Issue introduced in 4.15 with commit fab957c11efe2f405e08b9f0d080524bc2631428 and fixed in 5.14.12 with commit f1c7aa87c423e765e3862349c2f095fdfccdd9b3 |
| Issue introduced in 4.15 with commit fab957c11efe2f405e08b9f0d080524bc2631428 and fixed in 5.15 with commit bb8958d5dc79acbd071397abb57b8756375fe1ce |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47414 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| arch/riscv/mm/cacheflush.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/427faa29e06f0709476ea1bd59758f997ec8b64e |
| https://git.kernel.org/stable/c/f1c7aa87c423e765e3862349c2f095fdfccdd9b3 |
| https://git.kernel.org/stable/c/bb8958d5dc79acbd071397abb57b8756375fe1ce |
