On Tue, 19 May 2020 15:44:42 +0200 Christoph Hellwig <h...@lst.de> wrote:
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 2f6737cc53e6c..82da20e712507 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1208,7 +1208,13 @@ fetch_store_strlen(unsigned long addr) > u8 c; > > do { > - ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && > + (unsigned long)addr < TASK_SIZE) { > + ret = probe_user_read(&c, > + (__force u8 __user *)addr + len, 1); > + } else { > + ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + } > len++; > } while (c && ret == 0 && len < MAX_STRING_SIZE); To avoid redundant check in the loop, we can use strnlen_user_nofault() out of the loop. Something like below. ... u8 c; if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && (unsigned long)addr < TASK_SIZE) { return strnlen_user_nofault((__force u8 __user *)addr, MAX_STRING_SIZE); do { ret = probe_kernel_read(&c, (u8 *)addr + len, 1); len++; } while (c && ret == 0 && len < MAX_STRING_SIZE); ... This must work because we must not have a string that continues across kernel space and user space. Thank you, -- Masami Hiramatsu <mhira...@kernel.org>