[PATCH -tip 1/1] x86/bpf: Fix BPF percpu accesses

[Brian Gerst <brgerst@gmail.com>]

Due to commit 9d7de2aa8b41 ("Use relative percpu offsets"), percpu
addresses went from positive offsets from the GSBASE to negative kernel
virtual addresses.  The BPF verifier has an optimization for x86-64 that
loads the address of cpu_number into a register, but was only doing a
32-bit load which truncates negative addresses.  Change it to a 64-bit
load so that the address is properly sign-extended.

Fixes: 9d7de2aa8b41 ("Use relative percpu offsets")
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 60611df77957..f4859516b190 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -21707,7 +21707,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 			 * way, it's fine to back out this inlining logic
 			 */
 #ifdef CONFIG_SMP
-			insn_buf[0] = BPF_MOV32_IMM(BPF_REG_0, (u32)(unsigned long)&pcpu_hot.cpu_number);
+			insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, (u32)(unsigned long)&pcpu_hot.cpu_number);
 			insn_buf[1] = BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0);
 			insn_buf[2] = BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0);
 			cnt = 3;
-- 
2.48.1