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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Joern Engel <joern@lazybastard.org>, yangerkun <yangerkun@huawei.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org, kernel-janitors@vger.kernel.org
Subject: [PATCH v2] mtd: phram: Prevent divide by zero bug in phram_setup()
Date: Fri, 21 Jan 2022 14:55:05 +0300	[thread overview]
Message-ID: <20220121115505.GI1978@kadam> (raw)

The problem is that "erasesize" is a uint64_t type so it might be
non-zero but the lower 32 bits are zero so when it's truncated,
"(uint32_t)erasesize", then that value is zero. This leads to a
divide by zero bug.

Avoid the bug by delaying the divide until after we have validated
that "erasesize" is non-zero and within the uint32_t range.

Fixes: dc2b3e5cbc80 ("mtd: phram: use div_u64_rem to stop overwrite len in phram_setup")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: edit the commit message

 drivers/mtd/devices/phram.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/devices/phram.c b/drivers/mtd/devices/phram.c
index 6ed6c51fac69..d503821a3e60 100644
--- a/drivers/mtd/devices/phram.c
+++ b/drivers/mtd/devices/phram.c
@@ -264,16 +264,20 @@ static int phram_setup(const char *val)
 		}
 	}
 
-	if (erasesize)
-		div_u64_rem(len, (uint32_t)erasesize, &rem);
-
 	if (len == 0 || erasesize == 0 || erasesize > len
-	    || erasesize > UINT_MAX || rem) {
+	    || erasesize > UINT_MAX) {
 		parse_err("illegal erasesize or len\n");
 		ret = -EINVAL;
 		goto error;
 	}
 
+	div_u64_rem(len, (uint32_t)erasesize, &rem);
+	if (rem) {
+		parse_err("len is not multiple of erasesize\n");
+		ret = -EINVAL;
+		goto error;
+	}
+
 	ret = register_device(name, start, len, (uint32_t)erasesize);
 	if (ret)
 		goto error;
-- 
2.20.1

WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Joern Engel <joern@lazybastard.org>, yangerkun <yangerkun@huawei.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org, kernel-janitors@vger.kernel.org
Subject: [PATCH v2] mtd: phram: Prevent divide by zero bug in phram_setup()
Date: Fri, 21 Jan 2022 14:55:05 +0300	[thread overview]
Message-ID: <20220121115505.GI1978@kadam> (raw)

The problem is that "erasesize" is a uint64_t type so it might be
non-zero but the lower 32 bits are zero so when it's truncated,
"(uint32_t)erasesize", then that value is zero. This leads to a
divide by zero bug.

Avoid the bug by delaying the divide until after we have validated
that "erasesize" is non-zero and within the uint32_t range.

Fixes: dc2b3e5cbc80 ("mtd: phram: use div_u64_rem to stop overwrite len in phram_setup")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: edit the commit message

 drivers/mtd/devices/phram.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/devices/phram.c b/drivers/mtd/devices/phram.c
index 6ed6c51fac69..d503821a3e60 100644
--- a/drivers/mtd/devices/phram.c
+++ b/drivers/mtd/devices/phram.c
@@ -264,16 +264,20 @@ static int phram_setup(const char *val)
 		}
 	}
 
-	if (erasesize)
-		div_u64_rem(len, (uint32_t)erasesize, &rem);
-
 	if (len == 0 || erasesize == 0 || erasesize > len
-	    || erasesize > UINT_MAX || rem) {
+	    || erasesize > UINT_MAX) {
 		parse_err("illegal erasesize or len\n");
 		ret = -EINVAL;
 		goto error;
 	}
 
+	div_u64_rem(len, (uint32_t)erasesize, &rem);
+	if (rem) {
+		parse_err("len is not multiple of erasesize\n");
+		ret = -EINVAL;
+		goto error;
+	}
+
 	ret = register_device(name, start, len, (uint32_t)erasesize);
 	if (ret)
 		goto error;
-- 
2.20.1

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

             reply	other threads:[~2022-01-21 11:55 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-21 11:55 Dan Carpenter [this message]
2022-01-21 11:55 ` [PATCH v2] mtd: phram: Prevent divide by zero bug in phram_setup() Dan Carpenter
2022-01-23 15:22 ` Miquel Raynal
2022-01-23 15:22   ` Miquel Raynal
2022-01-23 15:33   ` Miquel Raynal
2022-01-23 15:33     ` Miquel Raynal

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