Commit 4d59b6cc authored Feb 08, 2017 by Tejun Heo Committed by Linus Torvalds Feb 08, 2017

cpumask: use nr_cpumask_bits for parsing functions

Commit 513e3d2d ("cpumask: always use nr_cpu_ids in formatting and
parsing functions") converted both cpumask printing and parsing
functions to use nr_cpu_ids instead of nr_cpumask_bits.  While this was
okay for the printing functions as it just picked one of the two output
formats that we were alternating between depending on a kernel config,
doing the same for parsing wasn't okay.

nr_cpumask_bits can be either nr_cpu_ids or NR_CPUS.  We can always use
nr_cpu_ids but that is a variable while NR_CPUS is a constant, so it can
be more efficient to use NR_CPUS when we can get away with it.
Converting the printing functions to nr_cpu_ids makes sense because it
affects how the masks get presented to userspace and doesn't break
anything; however, using nr_cpu_ids for parsing functions can
incorrectly leave the higher bits uninitialized while reading in these
masks from userland.  As all testing and comparison functions use
nr_cpumask_bits which can be larger than nr_cpu_ids, the parsed cpumasks
can erroneously yield false negative results.

This made the taskstats interface incorrectly return -EINVAL even when
the inputs were correct.

Fix it by restoring the parse functions to use nr_cpumask_bits instead
of nr_cpu_ids.

Link: http://lkml.kernel.org/r/20170206182442.GB31078@htj.duckdns.org


Fixes: 513e3d2d ("cpumask: always use nr_cpu_ids in formatting and parsing functions")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Martin Steigerwald <martin.steigerwald@teamix.de>
Debugged-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: <stable@vger.kernel.org>	[4.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0911d004

include/linux/cpumask.h

+4 −4

Original line number	Diff line number	Diff line
		@@ -560,7 +560,7 @@ static inline void cpumask_copy(struct cpumask *dstp,
		static inline int cpumask_parse_user(const char __user *buf, int len,
		struct cpumask *dstp)
		{
		return bitmap_parse_user(buf, len, cpumask_bits(dstp), nr_cpu_ids);
		return bitmap_parse_user(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
		}

		/**
		@@ -575,7 +575,7 @@ static inline int cpumask_parselist_user(const char __user *buf, int len,
		struct cpumask *dstp)
		{
		return bitmap_parselist_user(buf, len, cpumask_bits(dstp),
		nr_cpu_ids);
		nr_cpumask_bits);
		}

		/**
		@@ -590,7 +590,7 @@ static inline int cpumask_parse(const char buf, struct cpumask dstp)
		char *nl = strchr(buf, '\n');
		unsigned int len = nl ? (unsigned int)(nl - buf) : strlen(buf);

		return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpu_ids);
		return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
		}

		/**
		@@ -602,7 +602,7 @@ static inline int cpumask_parse(const char buf, struct cpumask dstp)
		*/
		static inline int cpulist_parse(const char buf, struct cpumask dstp)
		{
		return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpu_ids);
		return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpumask_bits);
		}

		/**

Admin message