Fix crash on process name "(sd-pam)" (PR 16594).

info os processes -fsanitize=address error
https://sourceware.org/bugzilla/show_bug.cgi?id=16594

info os processes
=================================================================
==5795== ERROR: AddressSanitizer: heap-use-after-free on address
0x600600214974 at pc 0x757a92 bp 0x7fff95dd9f00 sp 0x7fff95dd9ef0
READ of size 4 at 0x600600214974 thread T0
    #0 0x757a91 in get_cores_used_by_process (.../gdb/gdb+0x757a91)

At least Fedora 20 has process(es):
 6678 ?        Ss     0:00 /usr/lib/systemd/systemd --user
 6680 ?        S      0:00  \_ (sd-pam)

and GDB "info os processes" crashes on it as /proc/6680/stat contains:

6680 ((sd-pam)) S 6678 6678 6678 0 -1 1077961024 33 0 0 0 0 0 0 0 20 0 1 0 18568 73768960 120 18446744073709551615 1 1
0 0 0 0 0 4096 0 18446744073709551615 0 0 17 6 0 0 0 0 0 0 0 0 0 0 0 0 0

and GDB fails to find the proper end of the process name "((sd-pam))".
Therefore it reads core number off-by-one (it reads 17 instead of 6) and
overruns the array.

(1) Make the process name parsing more foolproof.

(2) Do not trust the parsed number from /proc/PID/stat and verify it against
    the array size.

I noticed that 'ps' gets this right, so I've peeked at its
sources, and it just looks for the first ')' starting at
the end.

https://gitorious.org/procps/procps/source/dc072aced7250fed9b01fb05f0d672678752a63e:proc/readproc.c

Look for stat2proc.

Given ps does that, I believe the kernel won't ever be changed
in a way that would break it.  So it sounds like could do strrchr
from the end of stat just as well without worry, which is simpler.

gdb/
2014-02-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	PR gdb/16594
	* common/linux-osdata.c (linux_common_core_of_thread): Find the end of
	process name.
	(get_cores_used_by_process): New parameter num_cores, use it.
	(linux_xfer_osdata_processes): Pass num_cores to it.
	* linux-tdep.c (linux_info_proc, linux_fill_prpsinfo): Find the end of
	process name.

Message-ID: <20140217212826.GA15080@host2.jankratochvil.net>

1 files changed, 6 insertions, 10 deletions

diff --git a/gdb/common/linux-osdata.c b/gdb/common/linux-osdata.c
index 805850c..dae637b 100644
--- a/gdb/common/linux-osdata.c
+++ b/gdb/common/linux-osdata.c
@@ -96,11 +96,8 @@ linux_common_core_of_thread (ptid_t ptid)
 	}
     }
 
-  p = strchr (content, '(');
-
-  /* Skip ")".  */
-  if (p != NULL)
-    p = strchr (p, ')');
+  /* ps command also relies on no trailing fields ever contain ')'.  */
+  p = strrchr (content, ')');
   if (p != NULL)
     p++;
 
@@ -258,11 +255,10 @@ get_process_owner (uid_t *owner, PID_T pid)
 }
 
 /* Find the CPU cores used by process PID and return them in CORES.
-   CORES points to an array of at least sysconf(_SC_NPROCESSOR_ONLN)
-   elements.  */
+   CORES points to an array of NUM_CORES elements.  */
 
 static int
-get_cores_used_by_process (PID_T pid, int *cores)
+get_cores_used_by_process (PID_T pid, int *cores, const int num_cores)
 {
   char taskdir[sizeof ("/proc/") + MAX_PID_T_STRLEN + sizeof ("/task") - 1];
   DIR *dir;
@@ -286,7 +282,7 @@ get_cores_used_by_process (PID_T pid, int *cores)
 	  core = linux_common_core_of_thread (ptid_build ((pid_t) pid,
 							  (pid_t) tid, 0));
 
-	  if (core >= 0)
+	  if (core >= 0 && core < num_cores)
 	    {
 	      ++cores[core];
 	      ++task_count;
@@ -350,7 +346,7 @@ linux_xfer_osdata_processes (gdb_byte *readbuf,
 
 	      /* Find CPU cores used by the process.  */
 	      cores = (int *) xcalloc (num_cores, sizeof (int));
-	      task_count = get_cores_used_by_process (pid, cores);
+	      task_count = get_cores_used_by_process (pid, cores, num_cores);
 	      cores_str = (char *) xcalloc (task_count, sizeof ("4294967295") + 1);
 
 	      for (i = 0; i < num_cores && task_count > 0; ++i)