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authorHeiko Carstens <heiko.carstens@de.ibm.com>2014-05-14 09:48:21 +0200
committerDavid S. Miller <davem@davemloft.net>2014-05-14 16:10:16 -0400
commite84d2f8d2ae33c8215429824e1ecf24cbca9645e (patch)
treed57e9fdad41fb1060dfb3a58cbb1cc1c5786df29 /arch/s390/net
parentf5738e2ef88070ef1372e6e718124d88e9abe4ac (diff)
downloadlinux-e84d2f8d2ae33c8215429824e1ecf24cbca9645e.tar.gz
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: aa2d2c73c21f2 ("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>
Diffstat (limited to 'arch/s390/net')
-rw-r--r--arch/s390/net/bpf_jit_comp.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 452d3ebd9d0f..e9f8fa9337fe 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -811,7 +811,7 @@ static struct bpf_binary_header *bpf_alloc_binary(unsigned int bpfsize,
return NULL;
memset(header, 0, sz);
header->pages = sz / PAGE_SIZE;
- hole = sz - (bpfsize + sizeof(*header));
+ hole = min(sz - (bpfsize + sizeof(*header)), PAGE_SIZE - sizeof(*header));
/* Insert random number of illegal instructions before BPF code
* and make sure the first instruction starts at an even address.
*/