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@xxxxxxxxxxxxxxx
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@xxxxxxxxxxxxx>
---
drivers/char/tpm/eventlog/tpm2.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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;
}
--
1.8.3.1
