linux-kernel - [PATCH v3 7/7] x86/cfi,bpf: Fix bpf_exception

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Message-Id: <20231215092707.910319166@infradead.org>
Date: Fri, 15 Dec 2023 10:12:23 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: paul.walmsley@...ive.com,
 palmer@...belt.com,
 aou@...s.berkeley.edu,
 tglx@...utronix.de,
 mingo@...hat.com,
 bp@...en8.de,
 dave.hansen@...ux.intel.com,
 x86@...nel.org,
 hpa@...or.com,
 davem@...emloft.net,
 dsahern@...nel.org,
 daniel@...earbox.net,
 andrii@...nel.org,
 martin.lau@...ux.dev,
 song@...nel.org,
 yonghong.song@...ux.dev,
 john.fastabend@...il.com,
 kpsingh@...nel.org,
 sdf@...gle.com,
 haoluo@...gle.com,
 jolsa@...nel.org,
 Arnd Bergmann <arnd@...db.de>,
 samitolvanen@...gle.com,
 keescook@...omium.org,
 nathan@...nel.org,
 ndesaulniers@...gle.com,
 linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org,
 bpf@...r.kernel.org,
 linux-arch@...r.kernel.org,
 llvm@...ts.linux.dev,
 jpoimboe@...nel.org,
 joao@...rdrivepizza.com,
 mark.rutland@....com,
 peterz@...radead.org
Subject: [PATCH v3 7/7] x86/cfi,bpf: Fix bpf_exception_cb() signature

From: Alexei Starovoitov <alexei.starovoitov@...il.com>

As per the earlier patches, BPF sub-programs have bpf_callback_t
signature and CFI expects callers to have matching signature. This is
violated by bpf_prog_aux::bpf_exception_cb().

[peterz: Changelog]
Reported-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Alexei Starovoitov <alexei.starovoitov@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/CAADnVQ+Z7UcXXBBhMubhcMM=R-dExk-uHtfOLtoLxQ1XxEpqEA@mail.gmail.com
---
 include/linux/bpf.h  |    2 +-
 kernel/bpf/helpers.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1484,7 +1484,7 @@ struct bpf_prog_aux {
 	int cgroup_atype; /* enum cgroup_bpf_attach_type */
 	struct bpf_map *cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE];
 	char name[BPF_OBJ_NAME_LEN];
-	unsigned int (*bpf_exception_cb)(u64 cookie, u64 sp, u64 bp);
+	u64 (*bpf_exception_cb)(u64 cookie, u64 sp, u64 bp, u64, u64);
 #ifdef CONFIG_SECURITY
 	void *security;
 #endif
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2537,7 +2537,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
 	 * which skips compiler generated instrumentation to do the same.
 	 */
 	kasan_unpoison_task_stack_below((void *)(long)ctx.sp);
-	ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp);
+	ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp, 0, 0);
 	WARN(1, "A call to BPF exception callback should never return\n");
 }