From: Jiong Wang jiong.wang@netronome.com
[ Upstream commit 75672dda27bd00109a84cd975c17949ad9c45663 ]
Yauheni reported the following code do not work correctly on BE arches:
ALU_ARSH_X: DST = (u64) (u32) ((*(s32 *) &DST) >> SRC); CONT; ALU_ARSH_K: DST = (u64) (u32) ((*(s32 *) &DST) >> IMM); CONT;
and are causing failure of test_verifier test 'arsh32 on imm 2' on BE arches.
The code is taking address and interpreting memory directly, so is not endianness neutral. We should instead perform standard C type casting on the variable. A u64 to s32 conversion will drop the high 32-bit and reserve the low 32-bit as signed integer, this is all we want.
Fixes: 2dc6b100f928 ("bpf: interpreter support BPF_ALU | BPF_ARSH") Reported-by: Yauheni Kaliuta yauheni.kaliuta@redhat.com Reviewed-by: Jakub Kicinski jakub.kicinski@netronome.com Reviewed-by: Quentin Monnet quentin.monnet@netronome.com Signed-off-by: Jiong Wang jiong.wang@netronome.com Acked-by: Song Liu songliubraving@fb.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 06ba9c5f156b..932fd3fa5a5a 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1367,10 +1367,10 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) insn++; CONT; ALU_ARSH_X: - DST = (u64) (u32) ((*(s32 *) &DST) >> SRC); + DST = (u64) (u32) (((s32) DST) >> SRC); CONT; ALU_ARSH_K: - DST = (u64) (u32) ((*(s32 *) &DST) >> IMM); + DST = (u64) (u32) (((s32) DST) >> IMM); CONT; ALU64_ARSH_X: (*(s64 *) &DST) >>= SRC;