linux-kernel - [PATCH AUTOSEL 4.9 7/8] acct: fix potential integer overflow in encode_comp

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Date:   Sat, 17 Dec 2022 10:30:51 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Zheng Yejian <zhengyejian1@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Zhang Jinhao <zhangjinhao2@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, dave@...olabs.net,
        willy@...radead.org, tangmeng@...ontech.com
Subject: [PATCH AUTOSEL 4.9 7/8] acct: fix potential integer overflow in encode_comp_t()

From: Zheng Yejian <zhengyejian1@...wei.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@...wei.com>
Cc: Hanjun Guo <guohanjun@...wei.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Zhang Jinhao <zhangjinhao2@...wei.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/acct.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/acct.c b/kernel/acct.c
index 37f1dc696fbd..928ed84f50df 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -328,6 +328,8 @@ 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