diff options
| author | Luke Nelson <lukenels@cs.washington.edu> | 2020-04-22 10:36:30 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-05-02 17:26:00 +0200 |
| commit | f670ee4406978e573a86d5c8d5c1827d0d3d5461 (patch) | |
| tree | c75ef8cf82a140fdbb0bfc53c795c15c5cd88d9a | |
| parent | c9184b35e27e6e844efb1bc5b2b1bb5068cc2fc7 (diff) | |
| download | linux-stable-f670ee4406978e573a86d5c8d5c1827d0d3d5461.tar.gz linux-stable-f670ee4406978e573a86d5c8d5c1827d0d3d5461.tar.bz2 linux-stable-f670ee4406978e573a86d5c8d5c1827d0d3d5461.zip | |
bpf, x86_32: Fix clobbering of dst for BPF_JSET
commit 50fe7ebb6475711c15b3397467e6424e20026d94 upstream.
The current JIT clobbers the destination register for BPF_JSET BPF_X
and BPF_K by using "and" and "or" instructions. This is fine when the
destination register is a temporary loaded from a register stored on
the stack but not otherwise.
This patch fixes the problem (for both BPF_K and BPF_X) by always loading
the destination register into temporaries since BPF_JSET should not
modify the destination register.
This bug may not be currently triggerable as BPF_REG_AX is the only
register not stored on the stack and the verifier uses it in a limited
way.
Fixes: 03f5781be2c7b ("bpf, x86_32: add eBPF JIT compiler for ia32")
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Wang YanQing <udknight@gmail.com>
Link: https://lore.kernel.org/bpf/20200422173630.8351-2-luke.r.nels@gmail.com
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/net/bpf_jit_comp32.c | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 21df0b6d7be6..2eaf1900ba67 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -1970,8 +1970,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, goto emit_cond_jmp_signed; } case BPF_JMP | BPF_JSET | BPF_X: { - u8 dreg_lo = dstk ? IA32_EAX : dst_lo; - u8 dreg_hi = dstk ? IA32_EDX : dst_hi; + u8 dreg_lo = IA32_EAX; + u8 dreg_hi = IA32_EDX; u8 sreg_lo = sstk ? IA32_ECX : src_lo; u8 sreg_hi = sstk ? IA32_EBX : src_hi; @@ -1980,6 +1980,12 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, STACK_VAR(dst_lo)); EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EDX), STACK_VAR(dst_hi)); + } else { + /* mov dreg_lo,dst_lo */ + EMIT2(0x89, add_2reg(0xC0, dreg_lo, dst_lo)); + /* mov dreg_hi,dst_hi */ + EMIT2(0x89, + add_2reg(0xC0, dreg_hi, dst_hi)); } if (sstk) { @@ -1998,8 +2004,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, } case BPF_JMP | BPF_JSET | BPF_K: { u32 hi; - u8 dreg_lo = dstk ? IA32_EAX : dst_lo; - u8 dreg_hi = dstk ? IA32_EDX : dst_hi; + u8 dreg_lo = IA32_EAX; + u8 dreg_hi = IA32_EDX; u8 sreg_lo = IA32_ECX; u8 sreg_hi = IA32_EBX; @@ -2008,6 +2014,12 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, STACK_VAR(dst_lo)); EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EDX), STACK_VAR(dst_hi)); + } else { + /* mov dreg_lo,dst_lo */ + EMIT2(0x89, add_2reg(0xC0, dreg_lo, dst_lo)); + /* mov dreg_hi,dst_hi */ + EMIT2(0x89, + add_2reg(0xC0, dreg_hi, dst_hi)); } hi = imm32 & (1<<31) ? (u32)~0 : 0; |