X-Git-Url: http://git.monstr.eu/?a=blobdiff_plain;f=include%2Flinux%2Fcpumask.h;h=4592d08459417d1072321665967a71cde7556c3f;hb=9daee913dc8d15eb65e0ff560803ab1c28bb480b;hp=fe29ac7cc469c2ed9cfa04b71c34a2ea172e905f;hpb=691b592abb9a5f2b331969393bc06fcc8b564d3c;p=linux-2.6-microblaze.git

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index fe29ac7cc469..4592d0845941 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -1071,4 +1071,22 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask,
 	[0] =  1UL							\
 } }
 
+/*
+ * Provide a valid theoretical max size for cpumap and cpulist sysfs files
+ * to avoid breaking userspace which may allocate a buffer based on the size
+ * reported by e.g. fstat.
+ *
+ * for cpumap NR_CPUS * 9/32 - 1 should be an exact length.
+ *
+ * For cpulist 7 is (ceil(log10(NR_CPUS)) + 1) allowing for NR_CPUS to be up
+ * to 2 orders of magnitude larger than 8192. And then we divide by 2 to
+ * cover a worst-case of every other cpu being on one of two nodes for a
+ * very large NR_CPUS.
+ *
+ *  Use PAGE_SIZE as a minimum for smaller configurations.
+ */
+#define CPUMAP_FILE_MAX_BYTES  ((((NR_CPUS * 9)/32 - 1) > PAGE_SIZE) \
+					? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE)
+#define CPULIST_FILE_MAX_BYTES  (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS * 7)/2 : PAGE_SIZE)
+
 #endif /* __LINUX_CPUMASK_H */