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Two more tracing fixes

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- Have kprobes not use copy_from_user() to access kernel addresses,
    because kprobes can legitimately poke at bad kernel memory, which
    will fault. Copy from user code should never fault in kernel space.
    Using probe_mem_read() can handle kernel address space faulting.
 
  - Put back the entries counter in the tracing output that was accidentally
    removed.
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Merge tag 'trace-v5.0-rc4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "Two more tracing fixes

   - Have kprobes not use copy_from_user() to access kernel addresses,
     because kprobes can legitimately poke at bad kernel memory, which
     will fault. Copy from user code should never fault in kernel space.
     Using probe_mem_read() can handle kernel address space faulting.

   - Put back the entries counter in the tracing output that was
     accidentally removed"

* tag 'trace-v5.0-rc4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix number of entries in trace header
  kprobe: Do not use uaccess functions to access kernel memory that can fault
This commit is contained in:
Linus Torvalds 2019-02-18 09:40:16 -08:00
commit 10f4902173
2 changed files with 3 additions and 9 deletions
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2
kernel/trace/trace.c
View File

@ -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",

10
kernel/trace/trace_kprobe.c
View File

@ -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;
}