Tony Battersby wrote:
sg has the following problems related to device removal: * opening a sg fd races with removing a device * closing a sg fd races with removing a device * /proc/scsi/sg/* access races with removing a device * command completion races with removing a device * command completion races with closing a sg fd * can rmmod sg with active commands These problems can cause kernel oopses, memory-use-after-free, or double-free errors. This patch fixes these problems by using krefs to manage the lifetime of sg_device and sg_fd. Each command submitted to the midlevel holds a reference to sg_fd until the completion callback. This ensures that sg_fd doesn't go away if the fd is closed with commands still outstanding. sg_fd gets the reference of sg_device (with scsi_device) and also makes sure that the sg module doesn't go away. /proc/scsi/sg/* functions don't play nicely with krefs because they give information about sg_fds which have been closed but not yet freed due to still having outstanding commands and sg_devices which have been removed but not yet freed due to still being referenced by one or more sg_fds. To deal with this safely without removing functionality, /proc functions now access sg_device and sg_fd while holding a lock instead of using kref_get()/kref_put(). Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx> --- This version changes BUG_ON() to WARN_ON()/return as suggested by Stefan Richter. The second patch "[PATCH 2/2] sg: fix races with ioctl(SG_IO) (v2)" is still the same as before, so I am not resending it. sg.c | 418 ++++++++++++++++++++++++++++++++----------------------------------- 1 file changed, 201 insertions(+), 217 deletions(-) --- linux-2.6.29-rc2/drivers/scsi/sg.c.orig 2009-01-21 14:34:05.000000000 -0500 +++ linux-2.6.29-rc2/drivers/scsi/sg.c 2009-01-21 14:36:00.000000000 -0500
Tony, We seem to have consensus on this version (v6 20090121). Thanks for you work. Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
