From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>
Subject: [PATCH v2] /dev/mem: Bail out upon SIGKILL.
Date: Fri, 23 Aug 2019 13:11:19 +0900 [thread overview]
Message-ID: <1566533479-4390-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> (raw)
syzbot found that a thread can stall for minutes inside read_mem() or
write_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. Let's insert cond_resched() and SIGKILL check into iteration loop
of reading/writing /dev/mem and /dev/kmem.
[ 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 | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index b08dc50..cb8e653 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -140,6 +140,10 @@ static ssize_t read_mem(struct file *file, char __user *buf,
int allowed, probe;
sz = size_inside_page(p, count);
+ cond_resched();
+ err = -EINTR;
+ if (fatal_signal_pending(current))
+ goto failed;
err = -EPERM;
allowed = page_is_allowed(p >> PAGE_SHIFT);
@@ -218,6 +222,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
int allowed;
sz = size_inside_page(p, count);
+ cond_resched();
+ if (fatal_signal_pending(current))
+ return -EINTR;
allowed = page_is_allowed(p >> PAGE_SHIFT);
if (!allowed)
@@ -451,6 +458,9 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
#endif
while (low_count > 0) {
sz = size_inside_page(p, low_count);
+ cond_resched();
+ if (fatal_signal_pending(current))
+ return -EINTR;
/*
* On ia64 if a page has been mapped somewhere as
@@ -477,6 +487,11 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
return -ENOMEM;
while (count > 0) {
sz = size_inside_page(p, count);
+ cond_resched();
+ if (fatal_signal_pending(current)) {
+ err = -EINTR;
+ break;
+ }
if (!is_vmalloc_or_module_addr((void *)p)) {
err = -ENXIO;
break;
@@ -523,6 +538,9 @@ static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
void *ptr;
sz = size_inside_page(p, count);
+ cond_resched();
+ if (fatal_signal_pending(current))
+ return -EINTR;
/*
* On ia64 if a page has been mapped somewhere as uncached, then
@@ -581,6 +599,11 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
unsigned long sz = size_inside_page(p, count);
unsigned long n;
+ cond_resched();
+ if (fatal_signal_pending(current)) {
+ err = -EINTR;
+ break;
+ }
if (!is_vmalloc_or_module_addr((void *)p)) {
err = -ENXIO;
break;
--
1.8.3.1
reply other threads:[~2019-08-23 4:12 UTC|newest]
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