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[79.43.130.89]) by smtp.gmail.com with ESMTPSA id c8sm51844622wrx.42.2019.01.10.09.39.47 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 10 Jan 2019 09:39:48 -0800 (PST) Date: Thu, 10 Jan 2019 18:39:47 +0100 From: Andrea Righi To: Steven Rostedt , Masami Hiramatsu Cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: [PATCH] tracing/kprobes: fix NULL pointer dereference in trace_kprobe_create() Message-ID: <20190110173947.GA19243@xps-13> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It is possible to trigger a NULL pointer dereference by writing an incorrectly formatted string to krpobe_events (omitting the symbol). Example: echo "r:event_1 " >> /sys/kernel/debug/tracing/kprobe_events That triggers this: BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 #PF error: [normal kernel read fault] PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 6 PID: 1757 Comm: bash Not tainted 5.0.0-rc1+ #125 Hardware name: Dell Inc. XPS 13 9370/0F6P3V, BIOS 1.5.1 08/09/2018 RIP: 0010:kstrtoull+0x2/0x20 Code: 28 00 00 00 75 17 48 83 c4 18 5b 41 5c 5d c3 b8 ea ff ff ff eb e1 b8 de ff ff ff eb da e8 d6 36 bb ff 66 0f 1f 44 00 00 31 c0 <80> 3f 2b 55 48 89 e5 0f 94 c0 48 01 c7 e8 5c ff ff ff 5d c3 66 2e RSP: 0018:ffffb5d482e57cb8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff82b12720 RDX: ffffb5d482e57cf8 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffb5d482e57d70 R08: ffffa0c05e5a7080 R09: ffffa0c05e003980 R10: 0000000000000000 R11: 0000000040000000 R12: ffffa0c04fe87b08 R13: 0000000000000001 R14: 000000000000000b R15: ffffa0c058d749e1 FS: 00007f137c7f7740(0000) GS:ffffa0c05e580000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000497d46004 CR4: 00000000003606e0 Call Trace: ? trace_kprobe_create+0xb6/0x840 ? _cond_resched+0x19/0x40 ? _cond_resched+0x19/0x40 ? __kmalloc+0x62/0x210 ? argv_split+0x8f/0x140 ? trace_kprobe_create+0x840/0x840 ? trace_kprobe_create+0x840/0x840 create_or_delete_trace_kprobe+0x11/0x30 trace_run_command+0x50/0x90 trace_parse_run_command+0xc1/0x160 probes_write+0x10/0x20 __vfs_write+0x3a/0x1b0 ? apparmor_file_permission+0x1a/0x20 ? security_file_permission+0x31/0xf0 ? _cond_resched+0x19/0x40 vfs_write+0xb1/0x1a0 ksys_write+0x55/0xc0 __x64_sys_write+0x1a/0x20 do_syscall_64+0x5a/0x120 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fix by doing the proper argument check when a NULL symbol is passed in trace_kprobe_create(). Signed-off-by: Andrea Righi --- kernel/trace/trace_kprobe.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 5c19b8c41c7e..76410ceeff50 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -644,6 +644,8 @@ static int trace_kprobe_create(int argc, const char *argv[]) /* try to parse an address. if that fails, try to read the * input as a symbol. */ + if (!argv[1]) + return -EINVAL; if (kstrtoul(argv[1], 0, (unsigned long *)&addr)) { /* Check whether uprobe event specified */ if (strchr(argv[1], '/') && strchr(argv[1], ':')) -- 2.17.1