If seq_file .next function does not change position index,
read after non-zero lseek can generate unexpected output.
In case of /sys/kernel/security/tpm0/ascii_bios_measurements
and 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/tpm1.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/char/tpm/eventlog/tpm1.c b/drivers/char/tpm/eventlog/tpm1.c
index 739b1d9..2c96977 100644
--- a/drivers/char/tpm/eventlog/tpm1.c
+++ b/drivers/char/tpm/eventlog/tpm1.c
@@ -115,6 +115,7 @@ static void *tpm1_bios_measurements_next(struct seq_file *m, void *v,
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(struct seq_file *m, void *v,
((v + sizeof(struct tcpa_event) + converted_event_size) > limit))
return NULL;
- (*pos)++;
return v;
}
--
1.8.3.1
