[bpf] bpf, arm64: fix trampoline for BPF_TRAMP_F_CALL_ORIG

Commit Message

Puranjay Mohan July 11, 2024, 3:18 p.m. UTC

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")
Closes: https://lore.kernel.org/all/[e-mail]/
Signed-off-by: Puranjay Mohan <[e-mail]>
---
 arch/arm64/net/bpf_jit_comp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

[e-mail] July 11, 2024, 4 p.m. UTC | #1

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[e-mail]>:

On Thu, 11 Jul 2024 15:18:38 +0000 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [bpf] bpf, arm64: fix trampoline for BPF_TRAMP_F_CALL_ORIG
    https://git.kernel.org/bpf/bpf-next/c/19d3c179a377

You are awesome, thank you!

Michael Aug. 17, 2024, 10:44 p.m. UTC | #2

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Patch

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 720336d28856..1bf483ec971d 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2141,7 +2141,7 @@  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);
 	}
 
@@ -2185,7 +2185,7 @@  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);
 	}