[patch 03/30] kallsyms: fix segfault in prefix_underscores_count()

[Greg KH]

2.6.30-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Paul Mundt <lethal@xxxxxxxxxxxx>

commit a9ece53c4089ef23d4002d34c4c7148d94622a40 upstream.

Commit b478b782e110fdb4135caa3062b6d687e989d994 "kallsyms, tracing: output
more proper symbol name" introduces a "bugfix" that introduces a segfault
in kallsyms in my configurations.

The cause is the introduction of prefix_underscores_count() which attempts
to count underscores, even in symbols that do not have them.  As a result,
it just uselessly runs past the end of the buffer until it crashes:

  CC      init/version.o
  LD      init/built-in.o
  LD      .tmp_vmlinux1
  KSYM    .tmp_kallsyms1.S
/bin/sh: line 1: 16934 Done                    sh-linux-gnu-nm -n .tmp_vmlinux1
     16935 Segmentation fault      | scripts/kallsyms > .tmp_kallsyms1.S
make: *** [.tmp_kallsyms1.S] Error 139

This simplifies the logic and just does a straightforward count.

Signed-off-by: Paul Mundt <lethal@xxxxxxxxxxxx>
Reviewed-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Paulo Marques <pmarques@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 scripts/kallsyms.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -539,7 +539,7 @@ static int prefix_underscores_count(cons
 {
 	const char *tail = str;
 
-	while (*tail != '_')
+	while (*tail == '_')
 		tail++;
 
 	return tail - str;


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