On Thu, 17 Jan 2019 15:13:09 +0900 Masami Hiramatsu <mhira...@kernel.org> wrote:
> On Wed, 16 Jan 2019 11:16:07 +0100 > Andreas Ziegler <andreas.zieg...@fau.de> wrote: > > > > > I went into this a bit deeper today, and right now it is simply failing > > to parse the code because there is no FETCH_OP_COMM case in > > process_fetch_insn() for uprobes so that will return -EILSEQ, leading to > > a make_data_loc(0, ...) in store_trace_args(). If we just add > > FETCH_OP_COMM and let val point to current->comm (that's what > > trace_kprobe.c does), we get an -EFAULT return value from > > fetch_store_string because strncpy_from_user() checks if the argument is > > in user space. > > Correct. I missed to add OP_COMM support. And uprobe's fetch_store_string > is only for user space strings. > > > So I think we might need a special case for that, something like > > FETCH_OP_ST_COMM_STRING which is only used for FETCH_OP_COMM and copies > > current->comm over to the dynamic area. The implementation could be > > similar to the old fetch_comm_string implementation before your rewrite. > > Hmm, instead, I would like to add current->comm checker and only allows > to copy that. That would be simpler and enough. > > Could you test below patch? > > > tracing: uprobes: Re-enable $comm support for uprobe events > > From: Masami Hiramatsu <mhira...@kernel.org> > > Since commit 533059281ee5 ("tracing: probeevent: Introduce new > argument fetching code") dropped the $comm support from uprobe > events, this re-enable it. > > For $comm support, use strncpy() instead of strncpy_from_user() > to copy current task's comm. Because it is in the kernel space, > strncpy_from_user() always fails to copy the comm. > This also use strlen() instead of strlen_user() to measure the > length of the comm. > > Signed-off-by: Masami Hiramatsu <mhira...@kernel.org> > Reported-by: Andreas Ziegler <andreas.zieg...@fau.de> > --- > kernel/trace/trace_uprobe.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c > index e335576b9411..97d134e83e0f 100644 > --- a/kernel/trace/trace_uprobe.c > +++ b/kernel/trace/trace_uprobe.c > @@ -156,7 +156,10 @@ fetch_store_string(unsigned long addr, void *dest, void > *base) > if (unlikely(!maxlen)) > return -ENOMEM; > > - ret = strncpy_from_user(dst, src, maxlen); > + if (addr == (unsigned long)current->comm) > + ret = strlcpy(dst, current->comm, maxlen); > + else > + ret = strncpy_from_user(dst, src, maxlen); > if (ret >= 0) { > if (ret == maxlen) > dst[ret - 1] = '\0'; > @@ -173,7 +176,10 @@ fetch_store_strlen(unsigned long addr) > int len; > void __user *vaddr = (void __force __user *) addr; > > - len = strnlen_user(vaddr, MAX_STRING_SIZE); > + if (addr == (unsigned long)current->comm) > + len = strlen(current->comm); To balance with the strnlen_user, we must increse the len in this block. (strlen doesn't count the final '\0', but strnlen_user counts it) Thank you, > + else > + len = strnlen_user(vaddr, MAX_STRING_SIZE); > > return (len > MAX_STRING_SIZE) ? 0 : len; > } > @@ -213,6 +219,9 @@ process_fetch_insn(struct fetch_insn *code, struct > pt_regs *regs, void *dest, > case FETCH_OP_IMM: > val = code->immediate; > break; > + case FETCH_OP_COMM: > + val = (unsigned long)current->comm; > + break; > case FETCH_OP_FOFFS: > val = translate_user_vaddr(code->immediate); > break; -- Masami Hiramatsu <mhira...@kernel.org>