| Message ID | 16bde2d6-4208-e478-0ac3-163b5c3a1eaa@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] tpm: tpm1_bios_measurements_next should increase position index | expand |
On Thu, Jan 30, 2020 at 01:23:21PM +0300, Vasily Averin wrote: > If seq_file .next function does not change position index, > read after non-zero lseek can generate unexpected output. Is it unwanted or unexpected? Unexpected would be mean random output. I don't think that is the case. Please describe more throughly. > For /sys/kernel/security/tpm0/binary_bios_measurements: > 1) read after lseek beyond end of file generates whole last line. > 2) read after lseek to middle of last line generates > expected end of last line and unexpected whole last line once again. > > Cc: stable@vger.kernel.org > Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...") > No empty line here. > https://bugzilla.kernel.org/show_bug.cgi?id=206283 "Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283" /Jarkko
On 2/1/20 8:03 PM, Jarkko Sakkinen wrote: > On Thu, Jan 30, 2020 at 01:23:21PM +0300, Vasily Averin wrote: >> If seq_file .next function does not change position index, >> read after non-zero lseek can generate unexpected output. > > Is it unwanted or unexpected? Unexpected would be mean random > output. I don't think that is the case. Please describe more > throughly. If .next function does not change position index, following .show function will repeat output related to current position index. >> For /sys/kernel/security/tpm0/binary_bios_measurements: >> 1) read after lseek beyond end of file generates whole last line. >> 2) read after lseek to middle of last line generates >> expected end of last line and unexpected whole last line once again. >> >> Cc: stable@vger.kernel.org >> Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...") >> > No empty line here. > >> https://bugzilla.kernel.org/show_bug.cgi?id=206283 > > "Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283" > > /Jarkko >
On Mon, Feb 03, 2020 at 08:14:53AM +0300, Vasily Averin wrote: > On 2/1/20 8:03 PM, Jarkko Sakkinen wrote: > > On Thu, Jan 30, 2020 at 01:23:21PM +0300, Vasily Averin wrote: > >> If seq_file .next function does not change position index, > >> read after non-zero lseek can generate unexpected output. > > > > Is it unwanted or unexpected? Unexpected would be mean random > > output. I don't think that is the case. Please describe more > > throughly. > > If .next function does not change position index, > following .show function will repeat output related to current position index. Thank you. That is clear and concise. Then, please put that to the commit message instead of "unexpected output". /Jarkko
diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c index b9aeda1..e741b11 100644 --- a/drivers/char/tpm/eventlog/tpm2.c +++ b/drivers/char/tpm/eventlog/tpm2.c @@ -94,6 +94,7 @@ static void *tpm2_bios_measurements_next(struct seq_file *m, void *v, size_t event_size; void *marker; + (*pos)++; event_header = log->bios_event_log; if (v == SEQ_START_TOKEN) { @@ -118,7 +119,6 @@ static void *tpm2_bios_measurements_next(struct seq_file *m, void *v, if (((v + event_size) >= limit) || (event_size == 0)) return NULL; - (*pos)++; return v; }
If seq_file .next function does not change position index, read after non-zero lseek can generate unexpected output. For /sys/kernel/security/tpm0/binary_bios_measurements: 1) read after lseek beyond end of file generates whole last line. 2) read after lseek to middle of last line generates expected end of last line and unexpected whole last line once again. Cc: stable@vger.kernel.org Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...") https://bugzilla.kernel.org/show_bug.cgi?id=206283 Signed-off-by: Vasily Averin <vvs@virtuozzo.com> --- drivers/char/tpm/eventlog/tpm2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)