linux-kernel - [PATCH] mtd: sm_ftl: fix NULL pointer warning

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Date:   Tue,  7 Jan 2020 22:24:52 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>
Cc:     Oleksandr Natalenko <oleksandr@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Wenwen Wang <wenwen@...uga.edu>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mtd: sm_ftl: fix NULL pointer warning

With gcc -O3, we get a new warning:

In file included from arch/arm64/include/asm/processor.h:28,
                 from drivers/mtd/sm_ftl.c:8:
In function 'memset',
    inlined from 'sm_read_sector.constprop' at drivers/mtd/sm_ftl.c:250:3:
include/linux/string.h:411:9: error: argument 1 null where non-null expected [-Werror=nonnull]
  return __builtin_memset(p, c, size);

>From all I can tell, this cannot happen (the function is called
either with a NULL buffer or with a -1 block number but not both),
but adding a check makes it more robust and avoids the warning.

Fixes: mmtom ("init/Kconfig: enable -O3 for all arches")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/mtd/sm_ftl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/sm_ftl.c b/drivers/mtd/sm_ftl.c
index 4744bf94ad9a..b9f272408c4d 100644
--- a/drivers/mtd/sm_ftl.c
+++ b/drivers/mtd/sm_ftl.c
@@ -247,7 +247,8 @@ static int sm_read_sector(struct sm_ftl *ftl,
 
 	/* FTL can contain -1 entries that are by default filled with bits */
 	if (block == -1) {
-		memset(buffer, 0xFF, SM_SECTOR_SIZE);
+		if (buffer)
+			memset(buffer, 0xFF, SM_SECTOR_SIZE);
 		return 0;
 	}
 
-- 
2.20.0