netdev - [PATCH net-next 2/2] bpf: fix unlocking of jited image when module ronx not set

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Date:   Tue, 21 Feb 2017 16:09:34 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     davem@...emloft.net
Cc:     ast@...nel.org, labbott@...hat.com, eric.dumazet@...il.com,
        willemb@...gle.com, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next 2/2] bpf: fix unlocking of jited image when module ronx not set

Eric and Willem reported that they recently saw random crashes when
JIT was in use and bisected this to 74451e66d516 ("bpf: make jited
programs visible in traces"). Issue was that the consolidation part
added bpf_jit_binary_unlock_ro() that would unlock previously made
read-only memory back to read-write. However, DEBUG_SET_MODULE_RONX
cannot be used for this to test for presence of set_memory_*()
functions. We need to use ARCH_HAS_SET_MEMORY instead to fix this;
also add the corresponding bpf_jit_binary_lock_ro() to filter.h.

Fixes: 74451e66d516 ("bpf: make jited programs visible in traces")
Reported-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Willem de Bruijn <willemb@...gle.com>
Bisected-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
 arch/arm64/net/bpf_jit_comp.c |  2 +-
 arch/s390/net/bpf_jit_comp.c  |  2 +-
 arch/x86/net/bpf_jit_comp.c   |  2 +-
 include/linux/filter.h        | 13 +++++++++++--
 4 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 05d1210..a785554 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -898,7 +898,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 
 	bpf_flush_icache(header, ctx.image + ctx.idx);
 
-	set_memory_ro((unsigned long)header, header->pages);
+	bpf_jit_binary_lock_ro(header);
 	prog->bpf_func = (void *)ctx.image;
 	prog->jited = 1;
 
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index f1d0e62..b49c52a 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1327,7 +1327,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 			print_fn_code(jit.prg_buf, jit.size_prg);
 	}
 	if (jit.prg_buf) {
-		set_memory_ro((unsigned long)header, header->pages);
+		bpf_jit_binary_lock_ro(header);
 		fp->bpf_func = (void *) jit.prg_buf;
 		fp->jited = 1;
 	}
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 18a62e2..32322ce 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1165,7 +1165,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 
 	if (image) {
 		bpf_flush_icache(header, image + proglen);
-		set_memory_ro((unsigned long)header, header->pages);
+		bpf_jit_binary_lock_ro(header);
 		prog->bpf_func = (void *)image;
 		prog->jited = 1;
 	} else {
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0c1cc91..0c167fd 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -551,7 +551,7 @@ static inline bool bpf_prog_was_classic(const struct bpf_prog *prog)
 
 #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
 
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
 static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
 {
 	set_memory_ro((unsigned long)fp, fp->pages);
@@ -562,6 +562,11 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
 	set_memory_rw((unsigned long)fp, fp->pages);
 }
 
+static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
+{
+	set_memory_ro((unsigned long)hdr, hdr->pages);
+}
+
 static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)
 {
 	set_memory_rw((unsigned long)hdr, hdr->pages);
@@ -575,10 +580,14 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
 {
 }
 
+static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
+{
+}
+
 static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)
 {
 }
-#endif /* CONFIG_DEBUG_SET_MODULE_RONX */
+#endif /* CONFIG_ARCH_HAS_SET_MEMORY */
 
 static inline struct bpf_binary_header *
 bpf_jit_binary_hdr(const struct bpf_prog *fp)
-- 
1.9.3