[tip:sched/urgent] sched/core: Fix buffer overflow in cgroup2 property cpu.max

[tip-bot for Konstantin Khlebnikov <tipbot@zytor.com>]

Commit-ID:  4c47acd824aaaa8fc6dc519fb4e08d1522105b7a
Gitweb:     https://git.kernel.org/tip/4c47acd824aaaa8fc6dc519fb4e08d1522105b7a
Author:     Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
AuthorDate: Wed, 6 Mar 2019 20:11:42 +0300
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 Mar 2019 12:06:15 +0100

sched/core: Fix buffer overflow in cgroup2 property cpu.max

Add limit into sscanf format string for on-stack buffer.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 0d5936344f30 ("sched: Implement interface for cgroup unified hierarchy")
Link: https://lkml.kernel.org/r/155189230232.2620.13120481613524200065.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6b2c055564b5..b7a4afdc33cb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6943,7 +6943,7 @@ static int __maybe_unused cpu_period_quota_parse(char *buf,
 {
 	char tok[21];	/* U64_MAX */
 
-	if (!sscanf(buf, "%s %llu", tok, periodp))
+	if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
 		return -EINVAL;
 
 	*periodp *= NSEC_PER_USEC;