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Subject[PATCH v2 1/3] tracing: uprobes: Re-enable $comm support for uprobe events
Date
Since commit 533059281ee5 ("tracing: probeevent: Introduce new
argument fetching code") dropped the $comm support from uprobe
events, this re-enables it.

For $comm support, uses strlcpy() 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 uses strlen() instead of strnlen_user() to measure the
length of the comm.

Fixes: 533059281ee5 ("tracing: probeevent: Introduce new argument fetching code")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reported-by: Andreas Ziegler <andreas.ziegler@fau.de>
Acked-by: Andreas Ziegler <andreas.ziegler@fau.de>
---
kernel/trace/trace_uprobe.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 3a1d5ab6b4ba..b07e498ccbc6 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';
@@ -180,7 +183,12 @@ 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);
+ if (len)
+ len++;
+ } else
+ len = strnlen_user(vaddr, MAX_STRING_SIZE);

return (len > MAX_STRING_SIZE) ? 0 : len;
}
@@ -220,6 +228,9 @@ 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;
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