On Fri, Dec 01, 2017 at 01:46:07AM +0100, Jann Horn wrote: > Check whether inputs from userspace are too long (explicit length field too > big or string not null-terminated) to avoid out-of-bounds reads. > > As far as I can tell, this can at worst lead to very limited kernel heap > memory disclosure or oopses. > > This bug can be triggered by an unprivileged user even if the xt_bpf module > is not loaded: iptables is available in network namespaces, and the xt_bpf > module can be autoloaded. > > Triggering the bug with a classic BPF filter with fake length 0x1000 causes > the following KASAN report: > > ================================================================== > BUG: KASAN: slab-out-of-bounds in bpf_prog_create+0x84/0xf0 > Read of size 32768 at addr ffff8801eff2c494 by task test/4627 > > CPU: 0 PID: 4627 Comm: test Not tainted 4.15.0-rc1+ #1 > [...] > Call Trace: > dump_stack+0x5c/0x85 > print_address_description+0x6a/0x260 > kasan_report+0x254/0x370 > ? bpf_prog_create+0x84/0xf0 > memcpy+0x1f/0x50 > bpf_prog_create+0x84/0xf0 > bpf_mt_check+0x90/0xd6 [xt_bpf] > [...] > Allocated by task 4627: > kasan_kmalloc+0xa0/0xd0 > __kmalloc_node+0x47/0x60 > xt_alloc_table_info+0x41/0x70 [x_tables] > [...] > The buggy address belongs to the object at ffff8801eff2c3c0 > which belongs to the cache kmalloc-2048 of size 2048 > The buggy address is located 212 bytes inside of > 2048-byte region [ffff8801eff2c3c0, ffff8801eff2cbc0) > [...] > ================================================================== Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
