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authorMichael Holzheu <holzheu@linux.vnet.ibm.com>2015-05-21 15:39:31 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-06-25 09:39:18 +0200
commitb035b60ded132592055c0f9bd1cc280259c7de4b (patch)
tree8461f72909499a558b1ef89cde41d25ae0854fee /arch/s390/net
parentaefbef10e3ae6e2c6e3c54f906f10b34c73a2c66 (diff)
downloadlinux-b035b60ded132592055c0f9bd1cc280259c7de4b.tar.gz
s390/bpf: Fix backward jumps
Currently all backward jumps crash for JITed s390x eBPF programs with an illegal instruction program check and kernel panic. Because for negative values the opcode of the jump instruction is overriden by the negative branch offset an illegal instruction is generated by the JIT: 000003ff802da378: c01100000002 lgfi %r1,2 000003ff802da37e: fffffff52065 unknown <-- illegal instruction 000003ff802da384: b904002e lgr %r2,%r14 So fix this and mask the offset in order not to damage the opcode. Cc: stable@vger.kernel.org # 4.0+ Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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 d3766dd67e23..fee782acc2ee 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -250,7 +250,7 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
({ \
/* Branch instruction needs 6 bytes */ \
int rel = (addrs[i + off + 1] - (addrs[i + 1] - 6)) / 2;\
- _EMIT6(op1 | reg(b1, b2) << 16 | rel, op2 | mask); \
+ _EMIT6(op1 | reg(b1, b2) << 16 | (rel & 0xffff), op2 | mask); \
REG_SET_SEEN(b1); \
REG_SET_SEEN(b2); \
})