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After fixing the previous filter issue reported by Vince Weaver,

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I could not come up with a situation where the operand counter (cnt)
 could go below zero, so I added a WARN_ON_ONCE(cnt < 0). Vince was
 able to trigger that warn on with his fuzzer test, but didn't have
 a filter input that caused it.
 
 Later, Sasha Levin was able to trigger that same warning, and was
 able to give me the filter string that triggered it. It was simply
 a single operation ">".
 
 I wrapped the filtering code in a userspace program such that I could
 single step through the logic. With a single operator the operand
 counter can legitimately go below zero, and should be reported to the
 user as an error, but should not produce a kernel warning. The
 WARN_ON_ONCE(cnt < 0) should be just a "if (cnt < 0) break;" and the
 code following it will produce the error message for the user.
 
 While debugging this, I found that there was another bug that let
 the pointer to the filter string go beyond the filter string.
 This too was fixed.
 
 Finally, there was a typo in a stub function that only gets compiled
 if trace events is disabled but tracing is enabled (I'm not even sure
 that's possible).
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Merge tag 'trace-fixes-4.1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "This isn't my 4.2 pull request (yet).  I found a few more bugs that I
  would have sent to fix 4.1, but since 4.1 is already out, I'm sending
  this before sending my 4.2 request (which is ready to go).

  After fixing the previous filter issue reported by Vince Weaver, I
  could not come up with a situation where the operand counter (cnt)
  could go below zero, so I added a WARN_ON_ONCE(cnt < 0).  Vince was
  able to trigger that warn on with his fuzzer test, but didn't have a
  filter input that caused it.

  Later, Sasha Levin was able to trigger that same warning, and was able
  to give me the filter string that triggered it.  It was simply a
  single operation ">".

  I wrapped the filtering code in a userspace program such that I could
  single step through the logic.  With a single operator the operand
  counter can legitimately go below zero, and should be reported to the
  user as an error, but should not produce a kernel warning.  The
  WARN_ON_ONCE(cnt < 0) should be just a "if (cnt < 0) break;" and the
  code following it will produce the error message for the user.

  While debugging this, I found that there was another bug that let the
  pointer to the filter string go beyond the filter string.  This too
  was fixed.

  Finally, there was a typo in a stub function that only gets compiled
  if trace events is disabled but tracing is enabled (I'm not even sure
  that's possible)"

* tag 'trace-fixes-4.1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix typo from "static inlin" to "static inline"
  tracing/filter: Do not allow infix to exceed end of string
  tracing/filter: Do not WARN on operand count going below zero
This commit is contained in:
Linus Torvalds 2015-06-26 13:56:55 -07:00
commit fcbc1777ce
2 changed files with 10 additions and 2 deletions
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2
kernel/trace/trace.h
View File

@ -1312,7 +1312,7 @@ void trace_event_init(void);
void trace_event_enum_update(struct trace_enum_map **map, int len);
#else
static inline void __init trace_event_init(void) { }
static inlin void trace_event_enum_update(struct trace_enum_map **map, int len) { }
static inline void trace_event_enum_update(struct trace_enum_map **map, int len) { }
#endif
extern struct trace_iterator *tracepoint_print_iter;

10
kernel/trace/trace_events_filter.c
View File

@ -1056,6 +1056,9 @@ static void parse_init(struct filter_parse_state *ps,
static char infix_next(struct filter_parse_state *ps)
{
if (!ps->infix.cnt)
return 0;
ps->infix.cnt--;
return ps->infix.string[ps->infix.tail++];
@ -1071,6 +1074,9 @@ static char infix_peek(struct filter_parse_state *ps)
static void infix_advance(struct filter_parse_state *ps)
{
if (!ps->infix.cnt)
return;
ps->infix.cnt--;
ps->infix.tail++;
}
@ -1385,7 +1391,9 @@ static int check_preds(struct filter_parse_state *ps)
if (elt->op != OP_NOT)
cnt--;
n_normal_preds++;
WARN_ON_ONCE(cnt < 0);
/* all ops should have operands */
if (cnt < 0)
break;
}
if (cnt != 1 || !n_normal_preds || n_logical_preds >= n_normal_preds) {