[v2] keys: proc_keys_next should increase position index
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Message ID 22307ecd-3254-6077-8bc7-02693338b586@virtuozzo.com
State New
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  • [v2] keys: proc_keys_next should increase position index
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Commit Message

Vasily Averin Jan. 30, 2020, 10:16 a.m. UTC
If seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output:

$ dd if=/proc/keys bs=1  # full usual output
0f6bfdf5 I--Q---     2 perm 3f010000  1000  1000 user      4af2f79ab8848d0a: 740
1fb91b32 I--Q---     3 perm 1f3f0000  1000 65534 keyring   _uid.1000: 2
27589480 I--Q---     1 perm 0b0b0000     0     0 user      invocation_id: 16
2f33ab67 I--Q---   152 perm 3f030000     0     0 keyring   _ses: 2
33f1d8fa I--Q---     4 perm 3f030000  1000  1000 keyring   _ses: 1
3d427fda I--Q---     2 perm 3f010000  1000  1000 user      69ec44aec7678e5a: 740
3ead4096 I--Q---     1 perm 1f3f0000  1000 65534 keyring   _uid_ses.1000: 1
521+0 records in
521+0 records out
521 bytes copied, 0,00123769 s, 421 kB/s

$ dd if=/proc/keys bs=500 skip=1  # read after lseek in middle of last line
dd: /proc/keys: cannot skip to specified offset
g   _uid_ses.1000: 1        <<<< end of last line
3ead4096 I--Q---     1 perm 1f3f0000  1000 65534 keyring   _uid_ses.1000: 1
   <<<< and whole last lien again
0+1 records in
0+1 records out
97 bytes copied, 0,000135035 s, 718 kB/s

$ dd if=/proc/keys bs=1000 skip=1   # read after lseek beyond end of file
dd: /proc/keys: cannot skip to specified offset
3ead4096 I--Q---     1 perm 1f3f0000  1000 65534 keyring   _uid_ses.1000: 1
   <<<< generates last line
0+1 records in
0+1 records out
76 bytes copied, 0,000119981 s, 633 kB/s

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>
---
 security/keys/proc.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

David Howells Jan. 31, 2020, 5:19 p.m. UTC | #1
Vasily Averin <vvs@virtuozzo.com> wrote:

> If seq_file .next fuction does not change position index,

"function"

>    <<<< and whole last lien again

"line"

I can fix these up for you.

> https://bugzilla.kernel.org/show_bug.cgi?id=206283

I wonder if this should have a tag - it looks kind of out of place without
one, but I can't find one suggested.

David
Vasily Averin Feb. 1, 2020, 7:54 a.m. UTC | #2
On 1/31/20 8:19 PM, David Howells wrote:
> Vasily Averin <vvs@virtuozzo.com> wrote:
>> If seq_file .next fuction does not change position index,
> "function"
>>    <<<< and whole last lien again
> "line"
> 
> I can fix these up for you.

thank you!

>> https://bugzilla.kernel.org/show_bug.cgi?id=206283
> 
> I wonder if this should have a tag - it looks kind of out of place without
> one, but I can't find one suggested.

Some maintainers of another subsystems asked me to add 
Cc: stable@vger.kernel.org
Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...")
however frankly speaking I do not think it is required in this case.

Thank you,
	Vasily Averin

Patch
diff mbox series

diff --git a/security/keys/proc.c b/security/keys/proc.c
index 415f3f1..d0cde66 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -139,6 +139,8 @@  static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos)
 	n = key_serial_next(p, v);
 	if (n)
 		*_pos = key_node_serial(n);
+	else
+		(*_pos)++;
 	return n;
 }