From: Dmitry V. Levin <ldv@altlinux.org>
Date: Tue, 1 Aug 2017 20:59:48 +0000 (+0000)
Subject: printpath: do not fetch more than PATH_MAX bytes from tracee's memory
X-Git-Tag: v4.19~190
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d7a45f8dcce557f1c7b876dd22af8f2e7daf1bb1;p=strace

printpath: do not fetch more than PATH_MAX bytes from tracee's memory

The kernel does not copy more than PATH_MAX bytes from userspace
pathnames, treating non-NUL-terminated pathnames as ENAMETOOLONG.

* util.c (printpathn): Decrease buffer size to PATH_MAX.
(printpath): Specify PATH_MAX - 1 as the maximum pathname length
to match the kernel behaviour.  The underlying umovestr call will fetch
up to PATH_MAX bytes from tracee's memory, but no more than first
PATH_MAX - 1 bytes will be printed.
---

diff --git a/util.c b/util.c
index a08acc80..68e6cdec 100644
--- a/util.c
+++ b/util.c
@@ -715,7 +715,7 @@ print_quoted_cstring(const char *str, unsigned int size)
 void
 printpathn(struct tcb *const tcp, const kernel_ulong_t addr, unsigned int n)
 {
-	char path[PATH_MAX + 1];
+	char path[PATH_MAX];
 	int nul_seen;
 
 	if (!addr) {
@@ -741,7 +741,7 @@ void
 printpath(struct tcb *const tcp, const kernel_ulong_t addr)
 {
 	/* Size must correspond to char path[] size in printpathn */
-	printpathn(tcp, addr, PATH_MAX);
+	printpathn(tcp, addr, PATH_MAX - 1);
 }
 
 /*