Debian: CVE-2021-47414: linux -- security update

Debian: CVE-2021-47414: linux -- security update

Severity

4

CVSS

(AV:L/AC:M/Au:N/C:P/I:P/A:P)

Published

05/21/2024

Created

07/31/2024

Added

07/30/2024

Modified

07/30/2024

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.

Solution(s)

• debian-upgrade-linux

References

• https://attackerkb.com/topics/cve-2021-47414
• CVE - 2021-47414