On Thu, 2017-09-28 at 00:41 +0200, Jason A. Donenfeld wrote:

Drivers that use the start method for netlink dumping rely on dumpit
not
being called if start fails. For example, ila_xlat.c allocates memory
and assigns it to cb->args[0] in its start() function. It might fail
to
do that and return -ENOMEM instead. However, even when returning an
error, dumpit will be called, which, in the example above, quickly
dereferences the memory in cb->args[0], which will OOPS the kernel.
This
is but one example of how this goes wrong.

Since start() has always been a function with an int return type, it
therefore makes sense to use it properly, rather than ignoring it.
This
patch thus returns early and does not call dumpit() when start()
fails.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Reviewed-by: Johannes Berg <johannes@sipsolutions.net>


FWIW, I found another (indirect, via genetlink, like ila_xlat.c) in-
tree user that cares and expects the correct failure behaviour:

net/ipv6/seg6.c
	.start  = seg6_genl_dumphmac_start,

which can also have memory allocation failures. No others appear to
exist, afaict.

Either way, perhaps it's worth sending this to stable for that reason.

johannes