| Date | Thu, 01 Jul 2010 10:33:13 -0700 | From | Greg KH <> | Subject | [patch 007/164] cpumask: fix compat getaffinity |
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2.6.33-stable review patch. If anyone has any objections, please let me know.
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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
commit fa9dc265ace9774e62f0e31108e5f47911124bda upstream.
Commit a45185d2d "cpumask: convert kernel/compat.c" broke libnuma, which abuses sched_getaffinity to find out NR_CPUS in order to parse /sys/devices/system/node/node*/cpumap.
On NUMA systems with less than 32 possibly CPUs, the current compat_sys_sched_getaffinity now returns '4' instead of the actual NR_CPUS/8, which makes libnuma bail out when parsing the cpumap.
The libnuma call sched_getaffinity(0, bitmap, 4096) at first. It mean the libnuma expect the return value of sched_getaffinity() is either len argument or NR_CPUS. But it doesn't expect to return nr_cpu_ids.
Strictly speaking, userland requirement are
1) Glibc assume the return value mean the lengh of initialized of mask argument. E.g. if sched_getaffinity(1024) return 128, glibc make zero fill rest 896 byte. 2) Libnuma assume the return value can be used to guess NR_CPUS in kernel. It assume len-arg<NR_CPUS makes -EINVAL. But it try len=4096 at first and 4096 is always bigger than NR_CPUS. Then, if we remove strange min_length normalization, we never hit -EINVAL case.
sched_getaffinity() already solved this issue. This patch adapts compat_sys_sched_getaffinity() to match the non-compat case.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Arnd Bergmann <arnd@arndb.de> Reported-by: Ken Werner <ken.werner@web.de> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/compat.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-)
--- a/kernel/compat.c +++ b/kernel/compat.c @@ -494,29 +494,26 @@ asmlinkage long compat_sys_sched_getaffi { int ret; cpumask_var_t mask; - unsigned long *k; - unsigned int min_length = cpumask_size(); - if (nr_cpu_ids <= BITS_PER_COMPAT_LONG) - min_length = sizeof(compat_ulong_t); - - if (len < min_length) + if ((len * BITS_PER_BYTE) < nr_cpu_ids) + return -EINVAL; + if (len & (sizeof(compat_ulong_t)-1)) return -EINVAL; if (!alloc_cpumask_var(&mask, GFP_KERNEL)) return -ENOMEM; ret = sched_getaffinity(pid, mask); - if (ret < 0) - goto out; + if (ret == 0) { + size_t retlen = min_t(size_t, len, cpumask_size()); - k = cpumask_bits(mask); - ret = compat_put_bitmap(user_mask_ptr, k, min_length * 8); - if (ret == 0) - ret = min_length; - -out: + if (compat_put_bitmap(user_mask_ptr, cpumask_bits(mask), retlen * 8)) + ret = -EFAULT; + else + ret = retlen; + } free_cpumask_var(mask); + return ret; }
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