diff options
| author | Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> | 2019-08-26 22:13:25 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-10-05 12:27:54 +0200 |
| commit | 4e9518d21cf0244247b2386f11949fb4ccf38667 (patch) | |
| tree | 78245ba70c7b300a86debf7730308d24e1a8cf97 | |
| parent | b85938f66b6ef4680a06e3229c10f5d6353f53d9 (diff) | |
/dev/mem: Bail out upon SIGKILL.
commit 8619e5bdeee8b2c685d686281f2d2a6017c4bc15 upstream.
syzbot found that a thread can stall for minutes inside read_mem() or
write_mem() after that thread was killed by SIGKILL [1]. Reading from
iomem areas of /dev/mem can be slow, depending on the hardware.
While reading 2GB at one read() is legal, delaying termination of killed
thread for minutes is bad. Thus, allow reading/writing /dev/mem and
/dev/kmem to be preemptible and killable.
[ 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
Theoretically, reading/writing /dev/mem and /dev/kmem can become
"interruptible". But this patch chose "killable". Future patch will make
them "interruptible" so that we can revert to "killable" if some program
regressed.
[1] https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: stable <stable@vger.kernel.org>
Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/1566825205-10703-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/char/mem.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 23f52a897283..6ebe2b86d8eb 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -95,6 +95,13 @@ void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr) } #endif +static inline bool should_stop_iteration(void) +{ + if (need_resched()) + cond_resched(); + return fatal_signal_pending(current); +} + /* * This funcion reads the *physical* memory. The f_pos points directly to the * memory location. @@ -161,6 +168,8 @@ static ssize_t read_mem(struct file *file, char __user *buf, p += sz; count -= sz; read += sz; + if (should_stop_iteration()) + break; } *ppos += read; @@ -232,6 +241,8 @@ static ssize_t write_mem(struct file *file, const char __user *buf, p += sz; count -= sz; written += sz; + if (should_stop_iteration()) + break; } *ppos += written; @@ -443,6 +454,10 @@ static ssize_t read_kmem(struct file *file, char __user *buf, read += sz; low_count -= sz; count -= sz; + if (should_stop_iteration()) { + count = 0; + break; + } } } @@ -467,6 +482,8 @@ static ssize_t read_kmem(struct file *file, char __user *buf, buf += sz; read += sz; p += sz; + if (should_stop_iteration()) + break; } free_page((unsigned long)kbuf); } @@ -517,6 +534,8 @@ static ssize_t do_write_kmem(unsigned long p, const char __user *buf, p += sz; count -= sz; written += sz; + if (should_stop_iteration()) + break; } *ppos += written; @@ -568,6 +587,8 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, buf += sz; virtr += sz; p += sz; + if (should_stop_iteration()) + break; } free_page((unsigned long)kbuf); } |