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authorLinus Torvalds <torvalds@linux-foundation.org>2023-03-12 18:52:03 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2023-03-12 18:52:03 +0300
commite7304080e0e50d979ce9eaf694ad8283e2e539ea (patch)
treec95f649c015d04fcd8b964e9d244b5282f8c48eb /include
parent81ff855485a366a391dc3aed3942715e676ed132 (diff)
downloadlinux-e7304080e0e50d979ce9eaf694ad8283e2e539ea.tar.xz
cpumask: relax sanity checking constraints
The cpumask_check() was unnecessarily tight, and causes problems for the users of cpumask_next(). We have a number of users that take the previous return value of one of the bit scanning functions and subtract one to keep it in "range". But since the scanning functions end up returning up to 'small_cpumask_bits' instead of the tighter 'nr_cpumask_bits', the range really needs to be using that widened form. [ This "previous-1" behavior is also the reason we have all those comments about /* -1 is a legal arg here. */ and separate checks for that being ok. So we could have just made "small_cpumask_bits-1" be a similar special "don't check this" value. Tetsuo Handa even suggested a patch that only does that for cpumask_next(), since that seems to be the only actual case that triggers, but that all makes it even _more_ magical and special. So just relax the check ] One example of this kind of pattern being the 'c_start()' function in arch/x86/kernel/cpu/proc.c, but also duplicated in various forms on other architectures. Reported-by: syzbot+96cae094d90877641f32@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=96cae094d90877641f32 Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Link: https://lore.kernel.org/lkml/c1f4cc16-feea-b83c-82cf-1a1f007b7eb9@I-love.SAKURA.ne.jp/ Fixes: 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask optimizations") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cpumask.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 63d637d18e79..d4901ca8883c 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -147,7 +147,7 @@ static __always_inline void cpu_max_bits_warn(unsigned int cpu, unsigned int bit
/* verify cpu argument to cpumask_* operators */
static __always_inline unsigned int cpumask_check(unsigned int cpu)
{
- cpu_max_bits_warn(cpu, nr_cpumask_bits);
+ cpu_max_bits_warn(cpu, small_cpumask_bits);
return cpu;
}