Re: fs/pipe.c null pointer dereference

[Earl Chew]

Earl Chew wrote:
> Is this possible via /proc/pid/fd/* ?

The window for failure is small. It's easiest to reproduce
this problem by stalling pipe_rdwr_open() to open up the
window:

--- pipe.c.orig 2009-10-15 20:33:53.000000000 -0700
+++ pipe.c      2009-10-15 20:17:40.000000000 -0700
@@ -736,2 +736,3 @@
 {
+       msleep(100);
        mutex_lock(&inode->i_mutex);


With the failure window widened, it's easy to reproduce
the failure with:

--------------------------------------------------------------
#!/bin/sh

while : ; do
  { echo y ; sleep 1 ; } | { while read ; do echo z$REPLY; done ; } &
  PID=$!
  OUT=$(ps -efl | grep 'sleep 1' | grep -v grep |
       { read PID REST ; echo $PID; } )
  OUT="${OUT%% *}"
  DELAY=$((RANDOM * 1000 / 32768))
  usleep $((DELAY * 1000 + RANDOM % 1000 ))
  echo n > /proc/$OUT/fd/1
done
--------------------------------------------------------------


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