tpm_i2c_infineon: fix potential buffer overruns caused by bit glitches on the bus

Discrete TPMs are often connected over slow serial buses which, on
some platforms, can have glitches causing bit flips.  In all the
driver _recv() functions, we need to use a u32 to unmarshal the
response size, otherwise a bit flip of the 31st bit would cause the
expected variable to go negative, which would then try to read a huge
amount of data.  Also sanity check that the expected amount of data is
large enough for the TPM header.

Signed-off-by: Jeremy Boone <[email protected]>
Cc: [email protected]
Signed-off-by: James Bottomley <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: James Morris <[email protected]>

diff --git a/drivers/char/tpm/tpm_i2c_infineon.c b/drivers/char/tpm/tpm_i2c_infineon.c
index c1dd39eaaeebb1f474d2d9f8b0d1e98e3559f27f..6116cd05e2287999c69ea4c5432098f159a44379 100644 (file)
--- a/drivers/char/tpm/tpm_i2c_infineon.c
+++ b/drivers/char/tpm/tpm_i2c_infineon.c
@@ -473,7 +473,8 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
 static int tpm_tis_i2c_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 {
        int size = 0;
-       int expected, status;
+       int status;
+       u32 expected;
 
        if (count < TPM_HEADER_SIZE) {
                size = -EIO;
@@ -488,7 +489,7 @@ static int tpm_tis_i2c_recv(struct tpm_chip *chip, u8 *buf, size_t count)
        }
 
        expected = be32_to_cpu(*(__be32 *)(buf + 2));
-       if ((size_t) expected > count) {
+       if (((size_t) expected > count) || (expected < TPM_HEADER_SIZE)) {
                size = -EIO;
                goto out;
        }