[PATCH 5.9 665/757] mmc: sdio: Check for CISTPL_VERS_1 buffer size

[Greg Kroah-Hartman]

From: Pali Rohár <pali@xxxxxxxxxx>

[ Upstream commit 8ebe2607965d3e2dc02029e8c7dd35fbe508ffd0 ]

Before parsing CISTPL_VERS_1 structure check that its size is at least two
bytes to prevent buffer overflow.

Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200727133837.19086-2-pali@xxxxxxxxxx
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/mmc/core/sdio_cis.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/core/sdio_cis.c b/drivers/mmc/core/sdio_cis.c
index e0655278c5c32..3efaa9534a777 100644
--- a/drivers/mmc/core/sdio_cis.c
+++ b/drivers/mmc/core/sdio_cis.c
@@ -26,6 +26,9 @@ static int cistpl_vers_1(struct mmc_card *card, struct sdio_func *func,
 	unsigned i, nr_strings;
 	char **buffer, *string;
 
+	if (size < 2)
+		return 0;
+
 	/* Find all null-terminated (including zero length) strings in
 	   the TPLLV1_INFO field. Trailing garbage is ignored. */
 	buf += 2;
-- 
2.25.1