From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Wang Date: Thu, 20 Dec 2018 17:08:11 +0800 Subject: [LTP] [PATCH 2/2] readdir02: use invalid DIR stream descriptor In-Reply-To: <20181220090811.21514-1-liwang@redhat.com> References: <20181220090811.21514-1-liwang@redhat.com> Message-ID: <20181220090811.21514-2-liwang@redhat.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it Issue: On ppc64le and aarch64, when testing in NFS mountpoint, test process receives SIGSEGV when calling readdir on a DIR which has just been closed by closedir(). Unfortunately, ltp/readdir02.c handles SIGSEGV. This makes it hits SIGSEGV again in its cleanup function. So readdir02 hangs there hitting SEGV endlessly. That's because a DIR * is NOT a file descriptor. It's memory allocated by opendir() that contains libc internal information about the directory. closedir(test_dir) frees any memory associated with the open directory pointer test_dir. To then pass the freed dir pointer to readdir() is a use-after-free. It probably won't return EBADF, it will dereference freed memory and whatever happens after that is undefined. In this patch, I simply modify the test to use an exist FILE * stream to simulate the invalid directory stream descriptor. Then it won't hit the use-after-free issue any more. Also, the sighandler function has been dropped. Reported-by: Xiong Zhou Signed-off-by: Li Wang Cc: Dave Chinner Cc: Scott Mayhew --- testcases/kernel/syscalls/readdir/readdir02.c | 64 +++++++++++---------------- 1 file changed, 25 insertions(+), 39 deletions(-) diff --git a/testcases/kernel/syscalls/readdir/readdir02.c b/testcases/kernel/syscalls/readdir/readdir02.c index 441c4b431..21d00cb0a 100644 --- a/testcases/kernel/syscalls/readdir/readdir02.c +++ b/testcases/kernel/syscalls/readdir/readdir02.c @@ -36,59 +36,45 @@ #include #include "tst_test.h" +#include "tst_safe_stdio.h" + +#define TEST_FILE "readdir_file.txt" static void verify_readdir(void) { + FILE *fp; DIR *test_dir; struct dirent *dptr; - if ((test_dir = opendir(".")) == NULL) { - tst_res(TFAIL, "opendir(\".\") Failed, errno=%d : %s", - errno, strerror(errno)); - } else { - if (closedir(test_dir) < 0) { + fp = SAFE_FOPEN(TEST_FILE, "ab+"); + /* regard FILE * as an invalid directory stream descriptor */ + test_dir = (DIR *)fp; + + dptr = readdir(test_dir); + switch (errno) { + case EBADF: + tst_res(TPASS, + "expected failure - errno = %d : %s", + errno, strerror(errno)); + break; + default: + if (dptr != NULL) { tst_res(TFAIL, - "closedir(\".\") Failed, errno=%d : %s", - errno, strerror(errno)); + "call failed with an " + "unexpected error - %d : %s", + errno, + strerror(errno)); } else { - dptr = readdir(test_dir); - switch (errno) { - case EBADF: - tst_res(TPASS, - "expected failure - errno = %d : %s", - errno, strerror(errno)); - break; - default: - if (dptr != NULL) { - tst_brk(TFAIL, - "call failed with an " - "unexpected error - %d : %s", - errno, - strerror(errno)); - } else { - tst_res(TINFO, - "readdir() is not _required_ to fail, " - "errno = %d ", errno); - } - } + tst_res(TINFO, + "readdir() is not _required_ to fail, " + "errno = %d ", errno); } } -} -static void sighandler(int sig LTP_ATTRIBUTE_UNUSED) -{ - tst_res(TCONF, - "This system's implementation of closedir() " - "will not allow this test to execute properly."); -} - -static void setup(void) -{ - SAFE_SIGNAL(SIGSEGV, sighandler); + SAFE_FCLOSE(fp); } static struct tst_test test = { .needs_tmpdir = 1, - .setup = setup, .test_all = verify_readdir, }; -- 2.14.5