[patch] Make mkdirat_pre_check resolv the dirfd if dirfd != AT_FDCWD

0001-Patch-that-makes-mkdirat_pre_check-resolv-the-dirfd-.patch (text/plain), 2.49 KB, created by Xake on 2010-10-28 08:28:57 UTC

From 8c521d4f15072c16a6e41b474eaad174a2372e57 Mon Sep 17 00:00:00 2001
From: Peter Hjalmarsson <[e-mail]>
Date: Thu, 28 Oct 2010 09:50:04 +0200
Subject: [PATCH] Patch that makes mkdirat_pre_check resolv the dirfd if dirfd != AT_FDCWD

This patch makes sandbox handle mkdirat() if dirfd != AT_FDCWD
canonicalize resolvs from CWD, and since you cannot resolv anything
from /proc for AT_FSCWD we keep the canonicalize for those cases,
and in every other case resolv dirfd from /proc, and does our tests on that path.
---
 libsandbox/wrapper-funcs/mkdirat_pre_check.c |   36 +++++++++++++++++++++----
 1 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/libsandbox/wrapper-funcs/mkdirat_pre_check.c b/libsandbox/wrapper-funcs/mkdirat_pre_check.c
index c999e46..538a607 100644
--- a/libsandbox/wrapper-funcs/mkdirat_pre_check.c
+++ b/libsandbox/wrapper-funcs/mkdirat_pre_check.c
@@ -11,15 +11,39 @@ bool sb_mkdirat_pre_check(const char *func, const char *pathname, int dirfd)
 
 	save_errno();
 
-	/* XXX: need to check pathname with dirfd */
-	if (-1 == canonicalize(pathname, canonic))
-		/* see comments in check_syscall() */
-		if (ENAMETOOLONG != errno) {
+	if (dirfd == AT_FDCWD)
+	{
+		/* dirfd points to CWD, so we reasolv from there */
+		if (-1 == canonicalize(pathname, canonic))
+			/* see comments in check_syscall() */
+			if (ENAMETOOLONG != errno) {
+				if (is_env_on(ENV_SANDBOX_DEBUG))
+					SB_EINFO("EARLY FAIL", "  %s(%s) @ canonicalize: %s\n",
+						func, pathname, strerror(errno));
+				return false;
+			}
+	}
+	else 
+	{
+		/* dirfd does not point to cwd, so we need to resolv it using /proc */
+		/* more or less copy-paste from libsandbox.c::before_syscall() */
+
+		size_t at_len = sizeof(canonic) - 1 - 1 - (pathname ? strlen(pathname) : 0);
+		sprintf(canonic, "/proc/%i/fd/%i", trace_pid ? : getpid(), dirfd);
+		ssize_t ret = readlink(canonic, canonic, at_len);
+		if (ret == -1) {
 			if (is_env_on(ENV_SANDBOX_DEBUG))
-				SB_EINFO("EARLY FAIL", "  %s(%s) @ canonicalize: %s\n",
-					func, pathname, strerror(errno));
+				SB_EINFO("EARLY FAIL", "  %s(%s) @ sb_mkdirat_pre_check,FD_LOOKUP: %s\n",
+					func, canonic, strerror(errno));
+			/* If the fd isn't found, some guys (glibc) expect errno */
+			if (errno == ENOENT)
+				errno = EBADF;
 			return false;
 		}
+		canonic[ret] = '/';
+		canonic[ret + 1] = '\0';
+		strcat(canonic,pathname);
+	}
 
 	/* XXX: Hack to prevent errors if the directory exist, and are
 	 * not writable - we rather return EEXIST than fail.  This can
-- 
1.7.3.2