| From 830c137d480e1e9b7c5d92864cf8869b3c8bc7d5 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Thu, 16 Jul 2020 09:37:04 +1000 |
| Subject: powerpc/vdso: Fix vdso cpu truncation |
| |
| From: Milton Miller <miltonm@us.ibm.com> |
| |
| [ Upstream commit a9f675f950a07d5c1dbcbb97aabac56f5ed085e3 ] |
| |
| The code in vdso_cpu_init that exposes the cpu and numa node to |
| userspace via SPRG_VDSO incorrctly masks the cpu to 12 bits. This means |
| that any kernel running on a box with more than 4096 threads (NR_CPUS |
| advertises a limit of of 8192 cpus) would expose userspace to two cpu |
| contexts running at the same time with the same cpu number. |
| |
| Note: I'm not aware of any distro shipping a kernel with support for more |
| than 4096 threads today, nor of any system image that currently exceeds |
| 4096 threads. Found via code browsing. |
| |
| Fixes: 18ad51dd342a7eb09dbcd059d0b451b616d4dafc ("powerpc: Add VDSO version of getcpu") |
| Signed-off-by: Milton Miller <miltonm@us.ibm.com> |
| Signed-off-by: Anton Blanchard <anton@linux.ibm.com> |
| Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
| Link: https://lore.kernel.org/r/20200715233704.1352257-1-anton@ozlabs.org |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/powerpc/kernel/vdso.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c |
| index f38f26e844b64..1c07df1ad560e 100644 |
| --- a/arch/powerpc/kernel/vdso.c |
| +++ b/arch/powerpc/kernel/vdso.c |
| @@ -678,7 +678,7 @@ int vdso_getcpu_init(void) |
| node = cpu_to_node(cpu); |
| WARN_ON_ONCE(node > 0xffff); |
| |
| - val = (cpu & 0xfff) | ((node & 0xffff) << 16); |
| + val = (cpu & 0xffff) | ((node & 0xffff) << 16); |
| mtspr(SPRN_SPRG_VDSO_WRITE, val); |
| get_paca()->sprg_vdso = val; |
| |
| -- |
| 2.25.1 |
| |
