From 2c4f1fcbef0bc324830bc2fb1a264c08ec93dec5 Mon Sep 17 00:00:00 2001 From: Changbin Du Date: Fri, 25 Jan 2019 23:10:50 +0800 Subject: kprobe: Do not use uaccess functions to access kernel memory that can fault The userspace can ask kprobe to intercept strings at any memory address, including invalid kernel address. In this case, fetch_store_strlen() would crash since it uses general usercopy function, and user access functions are no longer allowed to access kernel memory. For example, we can crash the kernel by doing something as below: $ sudo kprobe 'p:do_sys_open +0(+0(%si)):string' [ 103.620391] BUG: GPF in non-whitelisted uaccess (non-canonical address?) [ 103.622104] general protection fault: 0000 [#1] SMP PTI [ 103.623424] CPU: 10 PID: 1046 Comm: cat Not tainted 5.0.0-rc3-00130-gd73aba1-dirty #96 [ 103.625321] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-2-g628b2e6-dirty-20190104_103505-linux 04/01/2014 [ 103.628284] RIP: 0010:process_fetch_insn+0x1ab/0x4b0 [ 103.629518] Code: 10 83 80 28 2e 00 00 01 31 d2 31 ff 48 8b 74 24 28 eb 0c 81 fa ff 0f 00 00 7f 1c 85 c0 75 18 66 66 90 0f ae e8 48 63 ca 89 f8 <8a> 0c 31 66 66 90 83 c2 01 84 c9 75 dc 89 54 24 34 89 44 24 28 48 [ 103.634032] RSP: 0018:ffff88845eb37ce0 EFLAGS: 00010246 [ 103.635312] RAX: 0000000000000000 RBX: ffff888456c4e5a8 RCX: 0000000000000000 [ 103.637057] RDX: 0000000000000000 RSI: 2e646c2f6374652f RDI: 0000000000000000 [ 103.638795] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 103.640556] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 [ 103.642297] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 103.644040] FS: 0000000000000000(0000) GS:ffff88846f000000(0000) knlGS:0000000000000000 [ 103.646019] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 103.647436] CR2: 00007ffc79758038 CR3: 0000000463360006 CR4: 0000000000020ee0 [ 103.649147] Call Trace: [ 103.649781] ? sched_clock_cpu+0xc/0xa0 [ 103.650747] ? do_sys_open+0x5/0x220 [ 103.651635] kprobe_trace_func+0x303/0x380 [ 103.652645] ? do_sys_open+0x5/0x220 [ 103.653528] kprobe_dispatcher+0x45/0x50 [ 103.654682] ? do_sys_open+0x1/0x220 [ 103.655875] kprobe_ftrace_handler+0x90/0xf0 [ 103.657282] ftrace_ops_assist_func+0x54/0xf0 [ 103.658564] ? __call_rcu+0x1dc/0x280 [ 103.659482] 0xffffffffc00000bf [ 103.660384] ? __ia32_sys_open+0x20/0x20 [ 103.661682] ? do_sys_open+0x1/0x220 [ 103.662863] do_sys_open+0x5/0x220 [ 103.663988] do_syscall_64+0x60/0x210 [ 103.665201] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 103.666862] RIP: 0033:0x7fc22fadccdd [ 103.668034] Code: 48 89 54 24 e0 41 83 e2 40 75 32 89 f0 25 00 00 41 00 3d 00 00 41 00 74 24 89 f2 b8 01 01 00 00 48 89 fe bf 9c ff ff ff 0f 05 <48> 3d 00 f0 ff ff 77 33 f3 c3 66 0f 1f 84 00 00 00 00 00 48 8d 44 [ 103.674029] RSP: 002b:00007ffc7972c3a8 EFLAGS: 00000287 ORIG_RAX: 0000000000000101 [ 103.676512] RAX: ffffffffffffffda RBX: 0000562f86147a21 RCX: 00007fc22fadccdd [ 103.678853] RDX: 0000000000080000 RSI: 00007fc22fae1428 RDI: 00000000ffffff9c [ 103.681151] RBP: ffffffffffffffff R08: 0000000000000000 R09: 0000000000000000 [ 103.683489] R10: 0000000000000000 R11: 0000000000000287 R12: 00007fc22fce90a8 [ 103.685774] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000 [ 103.688056] Modules linked in: [ 103.689131] ---[ end trace 43792035c28984a1 ]--- This can be fixed by using probe_mem_read() instead, as it can handle faulting kernel memory addresses, which kprobes can legitimately do. Link: http://lkml.kernel.org/r/20190125151051.7381-1-changbin.du@gmail.com Cc: stable@vger.kernel.org Fixes: 9da3f2b7405 ("x86/fault: BUG() when uaccess helpers fault on kernel addresses") Signed-off-by: Changbin Du Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_kprobe.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) (limited to 'kernel/trace') diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index d5fb09ebba8b..9eaf07f99212 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -861,22 +861,14 @@ static const struct file_operations kprobe_profile_ops = { static nokprobe_inline int fetch_store_strlen(unsigned long addr) { - mm_segment_t old_fs; int ret, len = 0; u8 c; - old_fs = get_fs(); - set_fs(KERNEL_DS); - pagefault_disable(); - do { - ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1); + ret = probe_mem_read(&c, (u8 *)addr + len, 1); len++; } while (c && ret == 0 && len < MAX_STRING_SIZE); - pagefault_enable(); - set_fs(old_fs); - return (ret < 0) ? ret : len; } -- cgit v1.2.3 From 9e7382153f80ba45a0bbcd540fb77d4b15f6e966 Mon Sep 17 00:00:00 2001 From: Quentin Perret Date: Thu, 14 Feb 2019 15:29:50 +0000 Subject: tracing: Fix number of entries in trace header The following commit 441dae8f2f29 ("tracing: Add support for display of tgid in trace output") removed the call to print_event_info() from print_func_help_header_irq() which results in the ftrace header not reporting the number of entries written in the buffer. As this wasn't the original intent of the patch, re-introduce the call to print_event_info() to restore the orginal behaviour. Link: http://lkml.kernel.org/r/20190214152950.4179-1-quentin.perret@arm.com Acked-by: Joel Fernandes Cc: stable@vger.kernel.org Fixes: 441dae8f2f29 ("tracing: Add support for display of tgid in trace output") Signed-off-by: Quentin Perret Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/trace') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index c521b7347482..c4238b441624 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3384,6 +3384,8 @@ static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file const char tgid_space[] = " "; const char space[] = " "; + print_event_info(buf, m); + seq_printf(m, "# %s _-----=> irqs-off\n", tgid ? tgid_space : space); seq_printf(m, "# %s / _----=> need-resched\n", -- cgit v1.2.3