Message ID | 20200715233704.1352257-1-anton@ozlabs.org (mailing list archive) |
---|---|
State | Accepted |
Commit | a9f675f950a07d5c1dbcbb97aabac56f5ed085e3 |
Headers | show |
Series | powerpc/vdso: Fix vdso cpu truncation | expand |
On Thu, 16 Jul 2020 09:37:04 +1000, Anton Blanchard wrote: > 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. Applied to powerpc/next. [1/1] powerpc/vdso: Fix vdso cpu truncation https://git.kernel.org/powerpc/c/a9f675f950a07d5c1dbcbb97aabac56f5ed085e3 cheers
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c index e0f4ba45b6cc..8dad44262e75 100644 --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -677,7 +677,7 @@ 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;