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authorPeter Huewe <peter.huewe@infineon.com>2012-09-27 16:09:33 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-21 09:17:12 -0700
commit39a088528efe15ad3e1309b710d27fa9e3739aef (patch)
parent8b9b3bf4e79b8f41fa910932885526c2d1083af9 (diff)
tpm: Propagate error from tpm_transmit to fix a timeout hang
commit abce9ac292e13da367bbd22c1f7669f988d931ac upstream. tpm_write calls tpm_transmit without checking the return value and assigns the return value unconditionally to chip->pending_data, even if it's an error value. This causes three bugs. So if we write to /dev/tpm0 with a tpm_param_size bigger than TPM_BUFSIZE=0x1000 (e.g. 0x100a) and a bufsize also bigger than TPM_BUFSIZE (e.g. 0x100a) tpm_transmit returns -E2BIG which is assigned to chip->pending_data as -7, but tpm_write returns that TPM_BUFSIZE bytes have been successfully been written to the TPM, altough this is not true (bug #1). As we did write more than than TPM_BUFSIZE bytes but tpm_write reports that only TPM_BUFSIZE bytes have been written the vfs tries to write the remaining bytes (in this case 10 bytes) to the tpm device driver via tpm_write which then blocks at /* cannot perform a write until the read has cleared either via tpm_read or a user_read_timer timeout */ while (atomic_read(&chip->data_pending) != 0) msleep(TPM_TIMEOUT); for 60 seconds, since data_pending is -7 and nobody is able to read it (since tpm_read luckily checks if data_pending is greater than 0) (#bug 2). After that the remaining bytes are written to the TPM which are interpreted by the tpm as a normal command. (bug #3) So if the last bytes of the command stream happen to be a e.g. tpm_force_clear this gets accidentally sent to the TPM. This patch fixes all three bugs, by propagating the error code of tpm_write and returning -E2BIG if the input buffer is too big, since the response from the tpm for a truncated value is bogus anyway. Moreover it returns -EBUSY to userspace if there is a response ready to be read. Signed-off-by: Peter Huewe <peter.huewe@infineon.com> Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 14 insertions, 7 deletions
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index b85ee76e4b42..65b9d6f99437 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1019,17 +1019,20 @@ ssize_t tpm_write(struct file *file, const char __user *buf,
size_t size, loff_t *off)
struct tpm_chip *chip = file->private_data;
- size_t in_size = size, out_size;
+ size_t in_size = size;
+ ssize_t out_size;
/* cannot perform a write until the read has cleared
- either via tpm_read or a user_read_timer timeout */
- while (atomic_read(&chip->data_pending) != 0)
- msleep(TPM_TIMEOUT);
- mutex_lock(&chip->buffer_mutex);
+ either via tpm_read or a user_read_timer timeout.
+ This also prevents splitted buffered writes from blocking here.
+ */
+ if (atomic_read(&chip->data_pending) != 0)
+ return -EBUSY;
if (in_size > TPM_BUFSIZE)
- in_size = TPM_BUFSIZE;
+ return -E2BIG;
+ mutex_lock(&chip->buffer_mutex);
if (copy_from_user
(chip->data_buffer, (void __user *) buf, in_size)) {
@@ -1039,6 +1042,10 @@ ssize_t tpm_write(struct file *file, const char __user *buf,
/* atomic tpm command send and result receive */
out_size = tpm_transmit(chip, chip->data_buffer, TPM_BUFSIZE);
+ if (out_size < 0) {
+ mutex_unlock(&chip->buffer_mutex);
+ return out_size;
+ }
atomic_set(&chip->data_pending, out_size);