linux-hardening - [PATCH 5.17-rc1 v2] eeprom: at25: Restore missing allocation

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Message-Id: <20220118182003.3385019-1-keescook@chromium.org>
Date:   Tue, 18 Jan 2022 10:20:03 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        Jiri Prchal <jiri.prchal@...ignal.cz>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Ralph Siemsen <ralph.siemsen@...aro.org>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH 5.17-rc1 v2] eeprom: at25: Restore missing allocation

The at25 driver regressed in v5.17-rc1 due to a broken conflict
resolution: the allocation of the object was accidentally removed. Restore
it.

This was found when building under CONFIG_FORTIFY_SOURCE=y and
-Warray-bounds, which complained about strncpy() being used against an
empty object:

In function 'strncpy',
    inlined from 'at25_fw_to_chip.constprop' at drivers/misc/eeprom/at25.c:312:2:
./include/linux/fortify-string.h:48:33: warning: '__builtin_strncpy' offset [0, 9] is out of the bounds [0, 0] [-Warray-bounds]
   48 | #define __underlying_strncpy    __builtin_strncpy
      |                                 ^
./include/linux/fortify-string.h:59:16: note: in expansion of macro '__underlying_strncpy'
   59 |         return __underlying_strncpy(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~~
In function 'strncpy',
    inlined from 'at25_fram_to_chip' at drivers/misc/eeprom/at25.c:373:2,
    inlined from 'at25_probe' at drivers/misc/eeprom/at25.c:453:10:
./include/linux/fortify-string.h:48:33: warning: '__builtin_strncpy' offset [0, 9] is out of the bounds [0, 0] [-Warray-bounds]
   48 | #define __underlying_strncpy    __builtin_strncpy
      |                                 ^
./include/linux/fortify-string.h:59:16: note: in expansion of macro '__underlying_strncpy'
   59 |         return __underlying_strncpy(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~~

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Jiri Prchal <jiri.prchal@...ignal.cz>
Fixes: af40d16042d6 ("Merge v5.15-rc5 into char-misc-next")
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Link: https://lore.kernel.org/lkml/CAHp75VdqK7h63fz-cPaQ2MGaVdaR2f1Fb5kKCZidUG3RwLsAVA@mail.gmail.com/
Signed-off-by: Kees Cook <keescook@...omium.org>
---
v1: https://lore.kernel.org/lkml/20220107232409.1331599-1-keescook@chromium.org/
v2:
 - remove strscpy() replacements (unrelated)
 - use sizeof(*at25) (Andy)
---
 drivers/misc/eeprom/at25.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index c3305bdda69c..bee727ed98db 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -440,6 +440,10 @@ static int at25_probe(struct spi_device *spi)
 		return -ENXIO;
 	}
 
+	at25 = devm_kzalloc(&spi->dev, sizeof(*at25), GFP_KERNEL);
+	if (!at25)
+		return -ENOMEM;
+
 	mutex_init(&at25->lock);
 	at25->spi = spi;
 	spi_set_drvdata(spi, at25);
-- 
2.30.2