[PATCH 1/1] broken perf tool on 4.4-rc1

From: Tong Zhang
Date: Sat Jan 30 2016 - 16:10:26 EST


reproduce:
lzto@objd ~ $ ~/linux/tools/perf/perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
lzto@objd ~ $ ~/linux/tools/perf/perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
Segmentation fault
lzto@objd ~ $

Upon further investigation, it seems that
commit 747a9b0a08ae ("Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")
breaks perf tool.

__list_del(): tools/include/linux/list.h does not check null pointer dereference

Signed-off-by: Tong Zhang <ztong@xxxxxx>
---
tools/include/linux/list.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/include/linux/list.h b/tools/include/linux/list.h
index 1da4238..1d644a0 100644
--- a/tools/include/linux/list.h
+++ b/tools/include/linux/list.h
@@ -85,8 +85,10 @@ static inline void list_add_tail(struct list_head *new, struct list_head *head)
*/
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
- next->prev = prev;
- WRITE_ONCE(prev->next, next);
+ if (next)
+ next->prev = prev;
+ if (prev)
+ WRITE_ONCE(prev->next, next);
}

/**
--
2.4.10