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| author | Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> | 2019-08-26 22:13:25 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@google.com> | 2019-10-06 12:24:41 +0200 |
| commit | d8d7791979c3d6045b0904ddf8e17970401a5a80 (patch) | |
| tree | c4767be9f4bb7b87b20dbf976dd5ceb45047e8bf | |
| parent | 8ae30abcd46b196ea598cef94c6c51cfbb5d5293 (diff) | |
| download | hikey-linaro-d8d7791979c3d6045b0904ddf8e17970401a5a80.tar.gz | |
/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@google.com>
Change-Id: I2ff2bf3b76c9d75a327fab1495a15eeda19cb7da
| -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 1d66230f7fb8..bc9fd1253d77 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -99,6 +99,13 @@ void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr) { } +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. @@ -165,6 +172,8 @@ static ssize_t read_mem(struct file *file, char __user *buf, p += sz; count -= sz; read += sz; + if (should_stop_iteration()) + break; } *ppos += read; @@ -236,6 +245,8 @@ 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); } |