diff options
| author | Milton Miller <miltonm@us.ibm.com> | 2020-07-16 09:37:04 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-07-16 13:12:47 +1000 |
| commit | a9f675f950a07d5c1dbcbb97aabac56f5ed085e3 (patch) | |
| tree | 4bc45d6637669d6ae3aa689cb2e347ea12782336 | |
| parent | 77ca3951cc37727ae8361d583a30da7a1b84e427 (diff) | |
powerpc/vdso: Fix vdso cpu truncation
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
| -rw-r--r-- | arch/powerpc/kernel/vdso.c | 2 |
1 files changed, 1 insertions, 1 deletions
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; |