| Message ID | 20181010133817.GA11485@embeddedor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | tpm: fix unused-value issues in tpm_try_transmit | expand |
On Wed, Oct 10, 2018 at 03:38:17PM +0200, Gustavo A. R. Silva wrote: > Currently, there are some values assigned to variable *rc*, which > are never actually used in any computation, because such variable > is updated at line 550, before they can be used: > > 549out: > 550 rc = tpm_go_idle(chip, flags); > 551 if (rc) > 552 goto out; > > Fix this by removing such assignments. Should this be done by not quashing rc during the error unwind rather than dropping the errors? Jason
On Wed, Oct 10, 2018 at 08:06:38AM -0600, Jason Gunthorpe wrote: > On Wed, Oct 10, 2018 at 03:38:17PM +0200, Gustavo A. R. Silva wrote: > > Currently, there are some values assigned to variable *rc*, which > > are never actually used in any computation, because such variable > > is updated at line 550, before they can be used: > > > > 549out: > > 550 rc = tpm_go_idle(chip, flags); > > 551 if (rc) > > 552 goto out; > > > > Fix this by removing such assignments. > > Should this be done by not quashing rc during the error unwind rather > than dropping the errors? Yeah.` Wondering if tpm_go_idle() should simply be a void-function i.e. issue just a warning inside (disclaimer: did not revisit its code when writing this). > Jason /Jarkko
> > On Wed, Oct 10, 2018 at 08:06:38AM -0600, Jason Gunthorpe wrote: > > On Wed, Oct 10, 2018 at 03:38:17PM +0200, Gustavo A. R. Silva wrote: > > > Currently, there are some values assigned to variable *rc*, which > > > are never actually used in any computation, because such variable is > > > updated at line 550, before they can be used: > > > > > > 549out: > > > 550 rc = tpm_go_idle(chip, flags); > > > 551 if (rc) > > > 552 goto out; > > > > > > Fix this by removing such assignments. > > > > Should this be done by not quashing rc during the error unwind rather > > than dropping the errors? > > Yeah.` > > Wondering if tpm_go_idle() should simply be a void-function i.e. issue just a > warning inside (disclaimer: did not revisit its code when writing this). We did have rather a long discussion about it when it was merged. There are two flows that may crash rc = tpm2_commit_space() but you still can need to rc = go_idle() which also may crash which may override the previous value. Frankly the second one is fatal, the stack will go out of sync. We may do void here as the stack will crash in a subsequent command. The 'goto out' is quite a bug, probably caused by code movement. Thanks Tomas
On Thu, Oct 11, 2018 at 01:27:58PM +0000, Winkler, Tomas wrote: > > > > On Wed, Oct 10, 2018 at 08:06:38AM -0600, Jason Gunthorpe wrote: > > > On Wed, Oct 10, 2018 at 03:38:17PM +0200, Gustavo A. R. Silva wrote: > > > > Currently, there are some values assigned to variable *rc*, which > > > > are never actually used in any computation, because such variable is > > > > updated at line 550, before they can be used: > > > > > > > > 549out: > > > > 550 rc = tpm_go_idle(chip, flags); > > > > 551 if (rc) > > > > 552 goto out; > > > > > > > > Fix this by removing such assignments. > > > > > > Should this be done by not quashing rc during the error unwind rather > > > than dropping the errors? > > > > Yeah.` > > > > Wondering if tpm_go_idle() should simply be a void-function i.e. issue just a > > warning inside (disclaimer: did not revisit its code when writing this). > > We did have rather a long discussion about it when it was merged. > There are two flows that may crash > rc = tpm2_commit_space() > > but you still can need to > > rc = go_idle() > > which also may crash which may override the previous value. > > Frankly the second one is fatal, the stack will go out of sync. > We may do void here as the stack will crash in a subsequent command. > > The 'goto out' is quite a bug, probably caused by code movement. I just looked at the code properly and noticed that there is a regression caused by 627448e85c76 ("tpm: separate cmd_ready/go_idle from runtime_pm") i.e. when tpm_go_idle() fails it loops back and retries tpm_go_idle(). /Jarkko
On Mon, 2018-10-15 at 13:41 +0300, Jarkko Sakkinen wrote: > On Thu, Oct 11, 2018 at 01:27:58PM +0000, Winkler, Tomas wrote: > > > > > > On Wed, Oct 10, 2018 at 08:06:38AM -0600, Jason Gunthorpe wrote: > > > > On Wed, Oct 10, 2018 at 03:38:17PM +0200, Gustavo A. R. Silva wrote: > > > > > Currently, there are some values assigned to variable *rc*, which > > > > > are never actually used in any computation, because such variable is > > > > > updated at line 550, before they can be used: > > > > > > > > > > 549out: > > > > > 550 rc = tpm_go_idle(chip, flags); > > > > > 551 if (rc) > > > > > 552 goto out; > > > > > > > > > > Fix this by removing such assignments. > > > > > > > > Should this be done by not quashing rc during the error unwind rather > > > > than dropping the errors? > > > > > > Yeah.` > > > > > > Wondering if tpm_go_idle() should simply be a void-function i.e. issue just a > > > warning inside (disclaimer: did not revisit its code when writing this). > > > > We did have rather a long discussion about it when it was merged. > > There are two flows that may crash > > rc = tpm2_commit_space() > > > > but you still can need to > > > > rc = go_idle() > > > > which also may crash which may override the previous value. > > > > Frankly the second one is fatal, the stack will go out of sync. > > We may do void here as the stack will crash in a subsequent command. > > > > The 'goto out' is quite a bug, probably caused by code movement. > > I just looked at the code properly and noticed that there is a regression > caused by 627448e85c76 ("tpm: separate cmd_ready/go_idle from > runtime_pm") i.e. when tpm_go_idle() fails it loops back and retries > tpm_go_idle(). Yes, that's what I said, this part code was moved forth but no the label. Tomas
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index 129f640..8062736 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -512,7 +512,6 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, if (chip->ops->req_canceled(chip, status)) { dev_err(&chip->dev, "Operation Canceled\n"); - rc = -ECANCELED; goto out; } @@ -522,7 +521,6 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, chip->ops->cancel(chip); dev_err(&chip->dev, "Operation Timed out\n"); - rc = -ETIME; goto out; out_recv: @@ -533,14 +531,12 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, "tpm_transmit: tpm_recv: error %d\n", rc); goto out; } else if (len < TPM_HEADER_SIZE) { - rc = -EFAULT; goto out; } - if (len != be32_to_cpu(header->length)) { - rc = -EFAULT; + if (len != be32_to_cpu(header->length)) goto out; - } + rc = tpm2_commit_space(chip, space, ordinal, buf, &len); if (rc)
Currently, there are some values assigned to variable *rc*, which are never actually used in any computation, because such variable is updated at line 550, before they can be used: 549out: 550 rc = tpm_go_idle(chip, flags); 551 if (rc) 552 goto out; Fix this by removing such assignments. Addresses-Coverity-ID: 1470245 ("Unused value") Addresses-Coverity-ID: 1470250 ("Unused value") Addresses-Coverity-ID: 1470251 ("Unused value") Fixes: 627448e85c76 ("tpm: separate cmd_ready/go_idle from runtime_pm") Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> --- drivers/char/tpm/tpm-interface.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)