| 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-2023-52761: riscv: VMAP_STACK overflow detection thread-safe |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| riscv: VMAP_STACK overflow detection thread-safe |
| |
| commit 31da94c25aea ("riscv: add VMAP_STACK overflow detection") added |
| support for CONFIG_VMAP_STACK. If overflow is detected, CPU switches to |
| `shadow_stack` temporarily before switching finally to per-cpu |
| `overflow_stack`. |
| |
| If two CPUs/harts are racing and end up in over flowing kernel stack, one |
| or both will end up corrupting each other state because `shadow_stack` is |
| not per-cpu. This patch optimizes per-cpu overflow stack switch by |
| directly picking per-cpu `overflow_stack` and gets rid of `shadow_stack`. |
| |
| Following are the changes in this patch |
| |
| - Defines an asm macro to obtain per-cpu symbols in destination |
| register. |
| - In entry.S, when overflow is detected, per-cpu overflow stack is |
| located using per-cpu asm macro. Computing per-cpu symbol requires |
| a temporary register. x31 is saved away into CSR_SCRATCH |
| (CSR_SCRATCH is anyways zero since we're in kernel). |
| |
| Please see Links for additional relevant disccussion and alternative |
| solution. |
| |
| Tested by `echo EXHAUST_STACK > /sys/kernel/debug/provoke-crash/DIRECT` |
| Kernel crash log below |
| |
| Insufficient stack space to handle exception!/debug/provoke-crash/DIRECT |
| Task stack: [0xff20000010a98000..0xff20000010a9c000] |
| Overflow stack: [0xff600001f7d98370..0xff600001f7d99370] |
| CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 |
| Hardware name: riscv-virtio,qemu (DT) |
| epc : __memset+0x60/0xfc |
| ra : recursive_loop+0x48/0xc6 [lkdtm] |
| epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff20000010a97e80 |
| gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff20000010a97e88 |
| t1 : 000000000000002e t2 : 3233206874706564 s0 : ff20000010a982b0 |
| s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 0000000000000000 |
| a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 0000000000000000 |
| a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007fffffffffff |
| s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff20000010a9be90 |
| s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00fffffff0aa3684 |
| s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffffff8a7cad10 |
| s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffffff815dbaf4 |
| t5 : ffffffff815dbab8 t6 : ff20000010a9bb48 |
| status: 0000000200000120 badaddr: ff20000010a97e88 cause: 000000000000000f |
| Kernel panic - not syncing: Kernel stack overflow |
| CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 |
| Hardware name: riscv-virtio,qemu (DT) |
| Call Trace: |
| [<ffffffff80006754>] dump_backtrace+0x30/0x38 |
| [<ffffffff808de798>] show_stack+0x40/0x4c |
| [<ffffffff808ea2a8>] dump_stack_lvl+0x44/0x5c |
| [<ffffffff808ea2d8>] dump_stack+0x18/0x20 |
| [<ffffffff808dec06>] panic+0x126/0x2fe |
| [<ffffffff800065ea>] walk_stackframe+0x0/0xf0 |
| [<ffffffff0163a752>] recursive_loop+0x48/0xc6 [lkdtm] |
| SMP: stopping secondary CPUs |
| ---[ end Kernel panic - not syncing: Kernel stack overflow ]--- |
| |
| The Linux kernel CVE team has assigned CVE-2023-52761 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.15 with commit 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 and fixed in 6.5.13 with commit 1493baaf09e3c1899959c8a107cd1207e16d1788 |
| Issue introduced in 4.15 with commit 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 and fixed in 6.6.3 with commit eff53aea3855f71992c043cebb1c00988c17ee20 |
| Issue introduced in 4.15 with commit 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 and fixed in 6.7 with commit be97d0db5f44c0674480cb79ac6f5b0529b84c76 |
| |
| 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-2023-52761 |
| 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/include/asm/asm-prototypes.h |
| arch/riscv/include/asm/asm.h |
| arch/riscv/include/asm/thread_info.h |
| arch/riscv/kernel/asm-offsets.c |
| arch/riscv/kernel/entry.S |
| arch/riscv/kernel/traps.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/1493baaf09e3c1899959c8a107cd1207e16d1788 |
| https://git.kernel.org/stable/c/eff53aea3855f71992c043cebb1c00988c17ee20 |
| https://git.kernel.org/stable/c/be97d0db5f44c0674480cb79ac6f5b0529b84c76 |
