diff options
| author | Pu Lehui <pulehui@huawei.com> | 2026-07-08 06:44:33 +0000 |
|---|---|---|
| committer | Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2026-07-21 20:18:56 +0200 |
| commit | 52fb1756ea1d2759dfef2d86245be00b05dac3a2 (patch) | |
| tree | f8e6d241981b43ed1baeb1e7d037d6b5aedafc51 | |
| parent | f3ab878594b57602aab2231d859f25ccc6b1a534 (diff) | |
riscv, bpf: Fix kernel stack corruption in tailcall with CFI
When CONFIG_CFI_CLANG is enabled, prog->bpf_func already skips the kcfi
instruction during setup. Including it again in the tailcall jump offset
causes it to jump over an extra 4 bytes, skipping the stack pointer
adjustment, which will result in kernel stack corruption.
Fixes: 30a59cc79754 ("riscv, bpf: Fix possible infinite tailcall when CONFIG_CFI_CLANG is enabled")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20260708064436.2971933-5-pulehui@huaweicloud.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
| -rw-r--r-- | arch/riscv/net/bpf_jit_comp64.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 2f06752fb036..cedf40927474 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -18,7 +18,6 @@ #define RV_MAX_REG_ARGS 8 #define RV_FENTRY_NINSNS 2 #define RV_FENTRY_NBYTES (RV_FENTRY_NINSNS * 4) -#define RV_KCFI_NINSNS (IS_ENABLED(CONFIG_CFI) ? 1 : 0) /* imm that allows emit_imm to emit max count insns */ #define RV_MAX_COUNT_IMM 0x7FFF7FF7FF7FF7FF @@ -272,8 +271,8 @@ static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx) if (!is_tail_call) emit_addiw(RV_REG_A0, RV_REG_A5, 0, ctx); emit_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA, - /* kcfi, fentry and TCC init insns will be skipped on tailcall */ - is_tail_call ? (RV_KCFI_NINSNS + RV_FENTRY_NINSNS + 1) * 4 : 0, + /* fentry and TCC init insns will be skipped on tailcall */ + is_tail_call ? (RV_FENTRY_NINSNS + 1) * 4 : 0, ctx); } @@ -2033,6 +2032,8 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog) /* emit kcfi type preamble immediately before the first insn */ emit_kcfi(is_subprog ? cfi_bpf_subprog_hash : cfi_bpf_hash, ctx); + /* bpf prog starts here as kcfi skipped during prog->bpf_func setup */ + /* nops reserved for auipc+jalr pair */ for (i = 0; i < RV_FENTRY_NINSNS; i++) emit(rv_nop(), ctx); |