On Fri, Mar 16, 2012 at 10:36 AM, Greg KH <greg@xxxxxxxxx> wrote: > > On Thu, Jan 12, 2012 at 01:57:11PM -0800, Paul Taysom wrote: > > A USB stick with a ext file system on it, would occasionally crash > > when the stick was pulled. > > > > The problem was a timer was being set on the Backing Device Interface, > > bdi, after the USB device had been removed and the bdi had been > > unregistered. The bdi would then be later reinitialized by zeroing > > the timer without removing from the timer from the timer queue. > > This would eventually result in a kernel crash (NULL ptr dereference). > > > > When the bdi is unregistered, the dev field is set to NULL. This > > indication is used by bdi_unregister to only unregister the device > > once. > > > > Fix: When the backing device is invalidated, the mapping > > backing_dev_info > > should be redirected to the default_backing_dev_info. > > > > Created 3 USB sticks with ext2, ext4 and one with both apple and DOS > > file systems on it. Inserted and removed USB sticks many times in random > > order. With out the bug fix, the kernel would soon crash. With the fix, > > it did not. Ran on both stumpy and amd64-generic. > > > > Signed-off-by: Paul Taysom <taysom@xxxxxxxxxxxx> > > Cc: Mandeep Baines <msb@xxxxxxxxxxxx> > > Cc: Greg KH <greg@xxxxxxxxx> > > Cc: Jens Axboe <axboe@xxxxxxxxx> > > Cc: Theodore Tso <tytso@xxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxx> > > Cc: <linux-usb@xxxxxxxxxxxxxxx> > > Cc: <linux-kernel@xxxxxxxxxxxxxxx> > > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > > Cc: <linux-fsdevel@xxxxxxxxxxxxxxx> > > Cc: <stable@xxxxxxxxxx> > > --- > > fs/block_dev.c | 1 + > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > diff --git a/fs/block_dev.c b/fs/block_dev.c > > index afe74dd..322cd05 100644 > > --- a/fs/block_dev.c > > +++ b/fs/block_dev.c > > @@ -110,6 +110,7 @@ void invalidate_bdev(struct block_device *bdev) > > * But, for the strange corners, lets be cautious > > */ > > cleancache_flush_inode(mapping); > > + mapping->backing_dev_info = &default_backing_dev_info; > > } > > EXPORT_SYMBOL(invalidate_bdev); > > What ever happened to this patch? Is it still needed? Can you still > reproduce the problem on Linus's tree and older kernels? > Never heard anything back. Ted supplied a partial fix in 3.2.6 (I believe) for just the ext4 file system. Who should I follow up with? Thanks, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
