Hi Kostik, * Konstantin Belousov <k...@freebsd.org> wrote: > Log: > Do not advance req->oldidx when sysctl_old_user returning an > error due to copyout failure or short buffer. > > The later breaks the usermode iterators of the sysctl results that pack > arbitrary number of variable-sized structures. Iterator expects that > kernel filled exactly oldlen bytes, and tries to interpret half-filled > or garbage structure at the end of the buffer. In particular, > kinfo_getfile(3) segfaulted. > > Reported and tested by: pho > MFC after: 3 weeks
Is it possible that this change introduces a regression? Right now
`pstat -t' gets stuck in an infinite loop. I've added the following
printf:
| Index: pstat.c
| ===================================================================
| --- pstat.c (revision 192128)
| +++ pstat.c (working copy)
| @@ -263,6 +263,7 @@
| if (errno != ENOMEM)
| err(1, "sysctlbyname()");
| len *= 2;
| + printf("Going to %zu\n", len);
| if ((xttys = realloc(xttys, len)) == NULL)
| err(1, "realloc()");
| }
pstat on -CURRENT prints:
| LINE INQ CAN LIN LOW OUTQ USE LOW COL SESS PGID STATE
| Going to 0
| Going to 0
| Going to 0
| ...
If I use the same patch on RELENG_6, I get the expected result:
| LINE RAW CAN OUT IHIWT ILOWT OHWT LWT COL STATE SESS PGID DISC
| Going to 272
| Going to 544
| Going to 1088
| Going to 2176
| Going to 4352
| Going to 8704
| sysmouse 0 0 0 0 0 0 0 0 - 0 0 term
| ...
So the problem is that sysctl overwrites the len argument with 0, even
if it returns back to userspace with ENOMEM.
I see we have two changes in sysctl. In theory it could also be related
to jhb@'s changes to sysctl locking, but I suspect it's less likely.
--
Ed Schouten <e...@80386.nl>
WWW: http://80386.nl/
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