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From: Hari Bathini <hbathini@linux.ibm.com>
To: naveen.n.rao@linux.ibm.com, jniethe5@gmail.com,
	christophe.leroy@csgroup.eu, mpe@ellerman.id.au, ast@kernel.org,
	daniel@iogearbox.net
Cc: paulus@samba.org, andrii@kernel.org, kafai@fb.com,
	songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com,
	kpsingh@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	Hari Bathini <hbathini@linux.ibm.com>,
	stable@vger.kernel.org
Subject: [PATCH] powerpc/bpf: fix write protecting JIT code
Date: Mon, 25 Oct 2021 11:26:49 +0530	[thread overview]
Message-ID: <20211025055649.114728-1-hbathini@linux.ibm.com> (raw)

Running program with bpf-to-bpf function calls results in data access
exception (0x300) with the below call trace:

    [c000000000113f28] bpf_int_jit_compile+0x238/0x750 (unreliable)
    [c00000000037d2f8] bpf_check+0x2008/0x2710
    [c000000000360050] bpf_prog_load+0xb00/0x13a0
    [c000000000361d94] __sys_bpf+0x6f4/0x27c0
    [c000000000363f0c] sys_bpf+0x2c/0x40
    [c000000000032434] system_call_exception+0x164/0x330
    [c00000000000c1e8] system_call_vectored_common+0xe8/0x278

as bpf_int_jit_compile() tries writing to write protected JIT code
location during the extra pass.

Fix it by holding off write protection of JIT code until the extra
pass, where branch target addresses fixup happens.

Cc: stable@vger.kernel.org
Fixes: 62e3d4210ac9 ("powerpc/bpf: Write protect JIT code")
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/net/bpf_jit_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index fcbf7a917c56..90ce75f0f1e2 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -241,8 +241,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 	fp->jited_len = alloclen;
 
 	bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + (bpf_hdr->pages * PAGE_SIZE));
-	bpf_jit_binary_lock_ro(bpf_hdr);
 	if (!fp->is_func || extra_pass) {
+		bpf_jit_binary_lock_ro(bpf_hdr);
 		bpf_prog_fill_jited_linfo(fp, addrs);
 out_addrs:
 		kfree(addrs);
-- 
2.31.1


WARNING: multiple messages have this Message-ID (diff)
From: Hari Bathini <hbathini@linux.ibm.com>
To: naveen.n.rao@linux.ibm.com, jniethe5@gmail.com,
	christophe.leroy@csgroup.eu, mpe@ellerman.id.au, ast@kernel.org,
	daniel@iogearbox.net
Cc: songliubraving@fb.com, netdev@vger.kernel.org,
	john.fastabend@gmail.com, andrii@kernel.org,
	stable@vger.kernel.org, kpsingh@kernel.org, paulus@samba.org,
	yhs@fb.com, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	kafai@fb.com, Hari Bathini <hbathini@linux.ibm.com>
Subject: [PATCH] powerpc/bpf: fix write protecting JIT code
Date: Mon, 25 Oct 2021 11:26:49 +0530	[thread overview]
Message-ID: <20211025055649.114728-1-hbathini@linux.ibm.com> (raw)

Running program with bpf-to-bpf function calls results in data access
exception (0x300) with the below call trace:

    [c000000000113f28] bpf_int_jit_compile+0x238/0x750 (unreliable)
    [c00000000037d2f8] bpf_check+0x2008/0x2710
    [c000000000360050] bpf_prog_load+0xb00/0x13a0
    [c000000000361d94] __sys_bpf+0x6f4/0x27c0
    [c000000000363f0c] sys_bpf+0x2c/0x40
    [c000000000032434] system_call_exception+0x164/0x330
    [c00000000000c1e8] system_call_vectored_common+0xe8/0x278

as bpf_int_jit_compile() tries writing to write protected JIT code
location during the extra pass.

Fix it by holding off write protection of JIT code until the extra
pass, where branch target addresses fixup happens.

Cc: stable@vger.kernel.org
Fixes: 62e3d4210ac9 ("powerpc/bpf: Write protect JIT code")
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/net/bpf_jit_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index fcbf7a917c56..90ce75f0f1e2 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -241,8 +241,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 	fp->jited_len = alloclen;
 
 	bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + (bpf_hdr->pages * PAGE_SIZE));
-	bpf_jit_binary_lock_ro(bpf_hdr);
 	if (!fp->is_func || extra_pass) {
+		bpf_jit_binary_lock_ro(bpf_hdr);
 		bpf_prog_fill_jited_linfo(fp, addrs);
 out_addrs:
 		kfree(addrs);
-- 
2.31.1


             reply	other threads:[~2021-10-25  5:57 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-25  5:56 Hari Bathini [this message]
2021-10-25  5:56 ` [PATCH] powerpc/bpf: fix write protecting JIT code Hari Bathini
2021-10-25  6:15 ` Naveen N. Rao
2021-10-25  6:15   ` Naveen N. Rao
2021-10-25 22:54   ` Daniel Borkmann
2021-10-25 22:54     ` Daniel Borkmann
2021-10-29  1:50     ` Michael Ellerman
2021-10-29  1:50       ` Michael Ellerman
2021-11-02 11:59       ` Naveen N. Rao
2021-11-02 11:59         ` Naveen N. Rao
2021-11-02 13:48         ` Michael Ellerman
2021-11-02 13:48           ` Michael Ellerman
2021-11-02 17:34           ` Andrii Nakryiko
2021-11-02 17:34             ` Andrii Nakryiko
2021-11-02 10:12 ` Michael Ellerman
2021-11-02 10:12   ` Michael Ellerman

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