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library: address an 'uninitialised value' VALGRIND bug 

Thanks to valgrind and his --track-origins=yes option,
the problem and solution was suggested as shown below.

[ and it was created in that commit referenced below ]

But, after attacking this problem by adding a memset()
call in pids.c, a 2nd valgrind oops, also shown below,
was encountered. The dynamically acquired 'cmd' again!

[ might help to explain why changes appear excessive ]

Reference(s):
. 1st valgrind discovery
==11111== Conditional jump or move depends on uninitialised value(s)
==11111==    at 0x13425D: stat2proc (readproc.c:582)
==11111==    by 0x137436: look_up_our_self (readproc.c:1613)
==11111==    by 0x132196: fatal_proc_unmounted (pids.c:1388)
==11111==    by 0x11BA4D: before (top.c:3580)
==11111==    by 0x127E10: main (top.c:7173)
==11111==  Uninitialised value was created by a stack allocation
==11111==    at 0x132165: fatal_proc_unmounted (pids.c:1381)

. Jul, 2022 - fatal_proc_unmounted refactored
commit 52bd019d8c

. 2nd valgrind discovery
==22222== 16 bytes in 1 blocks are definitely lost
==22222==    by 0x4A0E60E: strdup (strdup.c:42)
==22222==    by 0x133D00: stat2proc (readproc.c:587)
==22222==    by 0x136E67: look_up_our_self (readproc.c:1613)
==22222==    by 0x131BC7: fatal_proc_unmounted (pids.c:1390)
==22222==    by 0x11B7C6: before (top.c:3580)
==22222==    by 0x127828: main (top.c:7173)

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2022-09-07 00:00:00 -05:00 committed by Craig Small
parent a8f1c50d3a
commit 046883b9d3
3 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
library/include/readproc.h
View File

@ -281,7 +281,7 @@ PROCTAB *openproc(unsigned flags, ... /* pid_t *| uid_t *| dev_t *| char *[, int
// with the previous process or thread.
proc_t *readproc(PROCTAB *__restrict const PT, proc_t *__restrict p);
proc_t *readeither(PROCTAB *__restrict const PT, proc_t *__restrict x);
int look_up_our_self(proc_t *p);
int look_up_our_self(void);
void closeproc(PROCTAB *PT);
char **vectorize_this_str(const char *src);

3
library/pids.c
View File

@ -1381,11 +1381,10 @@ PROCPS_EXPORT struct pids_stack *fatal_proc_unmounted (
{
struct pids_fetch *fetched;
unsigned tid;
proc_t self;
/* this is very likely the *only* newlib function where the
context (pids_info) of NULL will ever be permitted */
if (!look_up_our_self(&self)
if (!look_up_our_self()
|| (!return_self))
return NULL;

7
library/readproc.c
View File

@ -1602,15 +1602,18 @@ void closeproc(PROCTAB *PT) {
//////////////////////////////////////////////////////////////////////////////////
int look_up_our_self(proc_t *p) {
int look_up_our_self(void) {
struct utlbuf_s ub = { NULL, 0 };
int rc = 0;
proc_t p;
memset(&p, 0, sizeof(proc_t));
if(file2str("/proc/self", "stat", &ub) == -1){
fprintf(stderr, "Error, do this: mount -t proc proc /proc\n");
_exit(47);
}
rc = stat2proc(ub.buf, p); // parse /proc/self/stat
rc = stat2proc(ub.buf, &p); // parse /proc/self/stat
free_acquired(&p);
free(ub.buf);
return !rc;
}