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Subject[PATCH] /dev/mem: Bail out upon SIGKILL when reading memory.
Date
syzbot found that a thread can stall for minutes inside read_mem()
after that thread was killed by SIGKILL [1]. Reading 2GB at one read()
is legal, but delaying termination of killed thread for minutes is bad.

[ 1335.912419][T20577] read_mem: sz=4096 count=2134565632
[ 1335.943194][T20577] read_mem: sz=4096 count=2134561536
[ 1335.978280][T20577] read_mem: sz=4096 count=2134557440
[ 1336.011147][T20577] read_mem: sz=4096 count=2134553344
[ 1336.041897][T20577] read_mem: sz=4096 count=2134549248

[1] https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>
---
drivers/char/mem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index b08dc50..0f7d4c4 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -135,7 +135,7 @@ static ssize_t read_mem(struct file *file, char __user *buf,
if (!bounce)
return -ENOMEM;

- while (count > 0) {
+ while (count > 0 && !fatal_signal_pending(current)) {
unsigned long remaining;
int allowed, probe;

--
1.8.3.1
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