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author | Peter Huewe <peter.huewe@infineon.com> | 2012-09-27 16:09:33 +0200 |
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committer | Kent Yoder <key@linux.vnet.ibm.com> | 2012-10-10 11:34:31 -0500 |
commit | abce9ac292e13da367bbd22c1f7669f988d931ac (patch) | |
tree | 58fa3636762edde8d00dccece060579d226ff104 /drivers | |
parent | bf5308344527d015ac9a6d2bda4ad4d40fd7d943 (diff) | |
download | linux-abce9ac292e13da367bbd22c1f7669f988d931ac.tar.gz linux-abce9ac292e13da367bbd22c1f7669f988d931ac.tar.bz2 linux-abce9ac292e13da367bbd22c1f7669f988d931ac.zip |
tpm: Propagate error from tpm_transmit to fix a timeout hang
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>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/char/tpm/tpm.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c index 6724615a4fdd..4caef331a705 100644 --- a/drivers/char/tpm/tpm.c +++ b/drivers/char/tpm/tpm.c @@ -1182,17 +1182,20 @@ 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)) { @@ -1202,6 +1205,10 @@ 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); mutex_unlock(&chip->buffer_mutex); |