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authorKees Cook <keescook@chromium.org>2019-04-01 12:06:07 -0700
committerJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>2019-06-24 23:57:49 +0300
commit782779b60faa2fc7ff609ac8ef938260fd792c0f (patch)
tree56c4d8f22366f244910bd96c4ed6e1b6b553cc7d /drivers/char
parentc88e40e07cd967dcdf37321a63ab6e8b0d881100 (diff)
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tpm: Actually fail on TPM errors during "get random"
A "get random" may fail with a TPM error, but those codes were returned as-is to the caller, which assumed the result was the number of bytes that had been written to the target buffer, which could lead to a kernel heap memory exposure and over-read. This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as before. [ 18.092103] tpm tpm0: A TPM error (379) occurred attempting get random [ 18.092106] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-64' (offset 0, size 379)! Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989 Reported-by: Phil Baker <baker1tex@gmail.com> Reported-by: Craig Robson <craig@zhatt.com> Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure") Cc: Laura Abbott <labbott@redhat.com> Cc: Tomas Winkler <tomas.winkler@intel.com> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Tomas Winkler <tomas.winkler@intel.com> Tested-by: Bartosz Szczepanek <bsz@semihalf.com> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/tpm/tpm1-cmd.c7
-rw-r--r--drivers/char/tpm/tpm2-cmd.c7
2 files changed, 10 insertions, 4 deletions
diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index 85dcf2654d11..faacbe1ffa1a 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -510,7 +510,7 @@ struct tpm1_get_random_out {
*
* Return:
* * number of bytes read
- * * -errno or a TPM return code otherwise
+ * * -errno (positive TPM return codes are masked to -EIO)
*/
int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
{
@@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
"attempting get random");
- if (rc)
+ if (rc) {
+ if (rc > 0)
+ rc = -EIO;
goto out;
+ }
out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 4de49924cfc4..d103545e4055 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -297,7 +297,7 @@ struct tpm2_get_random_out {
*
* Return:
* size of the buffer on success,
- * -errno otherwise
+ * -errno otherwise (positive TPM return codes are masked to -EIO)
*/
int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
{
@@ -324,8 +324,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
offsetof(struct tpm2_get_random_out,
buffer),
"attempting get random");
- if (err)
+ if (err) {
+ if (err > 0)
+ err = -EIO;
goto out;
+ }
out = (struct tpm2_get_random_out *)
&buf.data[TPM_HEADER_SIZE];