| Message ID | af9dcaa7-6e4f-281a-2bae-fb605cc55d2d@virtuozzo.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | keys: seq_file .next functions should increase position index | expand |
I don't see the effect you're talking about with /proc/keys. I see the following: [root@andromeda ~]# dd if=/proc/keys bs=40 skip=1 dd: /proc/keys: cannot skip to specified offset and then it follows up with the normal content with no obvious duplicates (the lines are numbered ascendingly in the first column). I think I may be being confused by what you mean by "the last line". David
On 1/27/20 2:39 PM, David Howells wrote: > I don't see the effect you're talking about with /proc/keys. I see the > following: > > [root@andromeda ~]# dd if=/proc/keys bs=40 skip=1 > dd: /proc/keys: cannot skip to specified offset > > and then it follows up with the normal content with no obvious duplicates (the > lines are numbered ascendingly in the first column). > > I think I may be being confused by what you mean by "the last line". on unpatched kernel $ uname -a Linux vvsx1 5.3.0-26-generic #28~18.04.1-Ubuntu SMP Wed Dec 18 16:40:14 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux $ dd if=/proc/keys bs=1 # VvS: 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 On patched kernel: [test@localhost ~]$ uname -a Linux localhost.localdomain 5.5.0-rc6-00151-gd8d014f #8 SMP Fri Jan 24 13:25:06 MSK 2020 x86_64 x86_64 x86_64 GNU/Linux [test@localhost ~]$ dd if=/proc/keys bs=1 06e8bec5 I--Q--- 4 perm 1f3f0000 1000 65534 keyring _uid.1000: empty 1b7ee8ed I--Q--- 11 perm 3f030000 1000 1000 keyring _ses: 1 2c1a365d I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 3f5823b4 I--Q--- 6 perm 3f030000 1000 1000 keyring _ses: 1 286+0 records in 286+0 records out 286 bytes copied, 0,000414581 s, 690 kB/s [test@localhost ~]$ dd if=/proc/keys bs=270 skip=1 # VvS: read after lseek in middle of last line dd: /proc/keys: cannot skip to specified offset yring _ses: 1 <<<< only end of last line was generated, as expected 0+1 records in 0+1 records out 16 bytes copied, 7,7199e-05 s, 207 kB/s [test@localhost ~]$ dd if=/proc/keys bs=1000 skip=1 # VvS: read after lseek beond end of file dd: /proc/keys: cannot skip to specified offset 0+0 records in <<<< nothing was generated, as expected 0+0 records out 0 bytes copied, 8,8036e-05 s, 0,0 kB/s
On Fri, 2020-01-24 at 09:25 +0300, Vasily Averin wrote: > if seq_file .next fuction does not change position index, > read after some lseek can generate unexpected output. > > https://bugzilla.kernel.org/show_bug.cgi?id=206283 > Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Similar comments as I gave here: https://patchwork.kernel.org/patch/11346943/ /Jarkko
On Mon, 2020-01-27 at 11:39 +0000, David Howells wrote: > I don't see the effect you're talking about with /proc/keys. I see the > following: > > [root@andromeda ~]# dd if=/proc/keys bs=40 skip=1 > dd: /proc/keys: cannot skip to specified offset > > and then it follows up with the normal content with no obvious duplicates (the > lines are numbered ascendingly in the first column). > > I think I may be being confused by what you mean by "the last line". > > David The commit message is completely lacking cause and effect. For similar TPM commit I gave the following remarks: https://patchwork.kernel.org/patch/11346943/ /Jarkko
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; }
if seq_file .next fuction does not change position index, read after some lseek can generate unexpected output. 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(+)