linux-kernel - [PATCH] tpm2: fix off-by-one comparison and out-of-bounds read error

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Date:   Mon, 20 Mar 2017 14:23:36 +0000
From:   Colin King <colin.king@...onical.com>
To:     Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        tpmdd-devel@...ts.sourceforge.net
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] tpm2: fix off-by-one comparison and out-of-bounds read error

From: Colin Ian King <colin.king@...onical.com>

The comparison of an out of range index into space->context_tbl is
off-by-one and should be using >= rather than > in the comparison.

Detected by CoverityScan, CID#1419694 ("Out-of-bounds read")

Fixes: 849246e7ce9ce ("tpm2: add session handle context saving and restoring to the space code")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/char/tpm/tpm2-space.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index d36d81e07076..009934269514 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -229,7 +229,7 @@ static bool tpm2_map_to_phandle(struct tpm_space *space, void *handle)
 	int i;
 
 	i = 0xFFFFFF - (vhandle & 0xFFFFFF);
-	if (i > ARRAY_SIZE(space->context_tbl) || !space->context_tbl[i])
+	if (i >= ARRAY_SIZE(space->context_tbl) || !space->context_tbl[i])
 		return false;
 
 	phandle = space->context_tbl[i];
-- 
2.11.0