diff options
author | Dan Carpenter <dan.carpenter@oracle.com> | 2018-06-20 14:08:00 +0300 |
---|---|---|
committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-12-08 20:54:07 -0500 |
commit | ca16b0fbb05242f18da9d810c07d3882ffed831c (patch) | |
tree | b48c71b974b5d1f18969ae01c7081e20bbbc1f29 /scripts/recordmcount.pl | |
parent | b0e21a61d3196762b61f43ae994ffd255f646774 (diff) |
tracing: Have trace_stack nr_entries compare not be so subtle
Dan Carpenter reviewed the trace_stack.c code and figured he found an off by
one bug.
"From reviewing the code, it seems possible for
stack_trace_max.nr_entries to be set to .max_entries and in that case we
would be reading one element beyond the end of the stack_dump_trace[]
array. If it's not set to .max_entries then the bug doesn't affect
runtime."
Although it looks to be the case, it is not. Because we have:
static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
{ [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
struct stack_trace stack_trace_max = {
.max_entries = STACK_TRACE_ENTRIES - 1,
.entries = &stack_dump_trace[0],
};
And:
stack_trace_max.nr_entries = x;
for (; x < i; x++)
stack_dump_trace[x] = ULONG_MAX;
Even if nr_entries equals max_entries, indexing with it into the
stack_dump_trace[] array will not overflow the array. But if it is the case,
the second part of the conditional that tests stack_dump_trace[nr_entries]
to ULONG_MAX will always be true.
By applying Dan's patch, it removes the subtle aspect of it and makes the if
conditional slightly more efficient.
Link: http://lkml.kernel.org/r/20180620110758.crunhd5bfep7zuiz@kili.mountain
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'scripts/recordmcount.pl')
0 files changed, 0 insertions, 0 deletions