Heiko Carstens e84d2f8d2a net: filter: s390: fix JIT address randomization ... This is the s390 variant of Alexei's JIT bug fix. (patch description below stolen from Alexei's patch) bpf_alloc_binary() adds 128 bytes of room to JITed program image and rounds it up to the nearest page size. If image size is close to page size (like 4000), it is rounded to two pages: round_up(4000 + 4 + 128) == 8192 then 'hole' is computed as 8192 - (4000 + 4) = 4188 If prandom_u32() % hole selects a number >= PAGE_SIZE - sizeof(*header) then kernel will crash during bpf_jit_free(): kernel BUG at arch/x86/mm/pageattr.c:887! Call Trace: [<ffffffff81037285>] change_page_attr_set_clr+0x135/0x460 [<ffffffff81694cc0>] ? _raw_spin_unlock_irq+0x30/0x50 [<ffffffff810378ff>] set_memory_rw+0x2f/0x40 [<ffffffffa01a0d8d>] bpf_jit_free_deferred+0x2d/0x60 [<ffffffff8106bf98>] process_one_work+0x1d8/0x6a0 [<ffffffff8106bf38>] ? process_one_work+0x178/0x6a0 [<ffffffff8106c90c>] worker_thread+0x11c/0x370 since bpf_jit_free() does: unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK; struct bpf_binary_header *header = (void *)addr; to compute start address of 'bpf_binary_header' and header->pages will pass junk to: set_memory_rw(addr, header->pages); Fix it by making sure that &header->image[prandom_u32() % hole] and &header are in the same page. Fixes: aa2d2c73c2 ("s390/bpf,jit: address randomize and write protect jit code") Reported-by: Alexei Starovoitov <ast@plumgrid.com> Cc: <stable@vger.kernel.org> # v3.11+ Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2014-05-14 16:10:16 -04:00
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bpf_jit_comp.c	net: filter: s390: fix JIT address randomization	2014-05-14 16:10:16 -04:00
bpf_jit.S	s390/bpf,jit: BPF Just In Time compiler for s390	2012-09-26 15:44:49 +02:00
Makefile	s390/bpf,jit: BPF Just In Time compiler for s390	2012-09-26 15:44:49 +02:00