[PATCH 5.5 121/257] tpm: tpm1_bios_measurements_next should increase position index

[Greg Kroah-Hartman]

From: Vasily Averin <vvs@xxxxxxxxxxxxx>

commit d7a47b96ed1102551eb7325f97937e276fb91045 upstream.

If .next function does not change position index,
following .show function will repeat output related
to current position index.

In case of /sys/kernel/security/tpm0/ascii_bios_measurements
and binary_bios_measurements:
1) read after lseek beyound 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@xxxxxxxxxxxxxxx # 4.19.x
Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/tpm/eventlog/tpm1.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/tpm/eventlog/tpm1.c
+++ b/drivers/char/tpm/eventlog/tpm1.c
@@ -115,6 +115,7 @@ static void *tpm1_bios_measurements_next
 	u32 converted_event_size;
 	u32 converted_event_type;
 
+	(*pos)++;
 	converted_event_size = do_endian_conversion(event->event_size);
 
 	v += sizeof(struct tcpa_event) + converted_event_size;
@@ -132,7 +133,6 @@ static void *tpm1_bios_measurements_next
 	    ((v + sizeof(struct tcpa_event) + converted_event_size) > limit))
 		return NULL;
 
-	(*pos)++;
 	return v;
 }