[PATCH 6.1 0959/1146] acct: fix potential integer overflow in encode_comp_t()

Greg Kroah-Hartman
2022-12-28T16:46:33Z

From: Zheng Yejian <zhengyejian1@huawei.com>

[ Upstream commit c5f31c655bcc01b6da53b836ac951c1556245305 ]

The integer overflow is descripted with following codes:
> 317 static comp_t encode_comp_t(u64 value)
> 318 {
> 319 int exp, rnd;
......
> 341 exp <<= MANTSIZE;
> 342 exp += value;
> 343 return exp;
> 344 }

Currently comp_t is defined as type of '__u16', but the variable 'exp' is
type of 'int', so overflow would happen when variable 'exp' in line 343 is
greater than 65535.

Link: https://lkml.kernel.org/r/20210515140631.369106-3-zhengyejian1@huawei.com
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhang Jinhao <zhangjinhao2@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/acct.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/kernel/acct.c b/kernel/acct.c
index 62200d799b9b..034a26daabb2 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -350,6 +350,8 @@ static comp_t encode_comp_t(unsigned long value)
exp++;
}

+ if (exp > (((comp_t) ~0U) >> MANTSIZE))
+ return (comp_t) ~0U;
/*
* Clean it up and polish it off.
*/
--
2.35.1