bpf, arm64: Fix trampoline for BPF_TRAMP_F_CALL_ORIG

When BPF_TRAMP_F_CALL_ORIG is set, the trampoline calls
__bpf_tramp_enter() and __bpf_tramp_exit() functions, passing them
the struct bpf_tramp_image *im pointer as an argument in R0.

The trampoline generation code uses emit_addr_mov_i64() to emit
instructions for moving the bpf_tramp_image address into R0, but
emit_addr_mov_i64() assumes the address to be in the vmalloc() space
and uses only 48 bits. Because bpf_tramp_image is allocated using
kzalloc(), its address can use more than 48-bits, in this case the
trampoline will pass an invalid address to __bpf_tramp_enter/exit()
causing a kernel crash.

Fix this by using emit_a64_mov_i64() in place of emit_addr_mov_i64()
as it can work with addresses that are greater than 48-bits.

Fixes: efc9909fdce0 ("bpf, arm64: Add bpf trampoline for arm64")
Signed-off-by: Puranjay Mohan <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Closes: https://lore.kernel.org/all/SJ0PR15MB461564D3F7E7A763498CA6A8CBDB2@SJ0PR15MB4615.namprd15.prod.outlook.com/
Link: https://lore.kernel.org/bpf/[email protected]

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 751331f5ba9061d258a07154552d1a31c48219fa..dd0bb069df4bbe3ef35ab19bb0f8bbf2e9ef163d 100644 (file)
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2147,7 +2147,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
        emit(A64_STR64I(A64_R(20), A64_SP, regs_off + 8), ctx);
 
        if (flags & BPF_TRAMP_F_CALL_ORIG) {
-               emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
+               emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
                emit_call((const u64)__bpf_tramp_enter, ctx);
        }
 
@@ -2191,7 +2191,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
 
        if (flags & BPF_TRAMP_F_CALL_ORIG) {
                im->ip_epilogue = ctx->ro_image + ctx->idx;
-               emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
+               emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
                emit_call((const u64)__bpf_tramp_exit, ctx);
        }