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Tests: TestProcFs cannot assume stdin/stdout/stderr are the same

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If someone runs the test with shell redirection going on, or in a way
that changes any of the standard file descriptors this assumption will
not hold. When running from a terminal normally, it is true however.

Instead, check that /proc/self/fd/[0,1,2] are symlinks, and can be
stat-d by verifying that both stat and lstat succeed, and give different
struct stat contents.
This commit is contained in:
Andrew Kaster 2021-06-27 21:16:21 -06:00 committed by Ali Mohammad Pur
parent 5e8a0c014e
commit 44a6715584
1 changed files with 30 additions and 12 deletions
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42
Tests/Kernel/TestProcFS.cpp
View file

@ -6,27 +6,45 @@
#include <LibTest/TestCase.h>
#include <cstring>
#include <sys/stat.h>
#include <unistd.h>
TEST_CASE(test_process_fd_readlink)
{
char expected_link[MAXPATHLEN];
char buf[MAXPATHLEN];
// Make sure that stdin, stdout and stderr are actually symlinks that point somewhere interesting
// Sadly we can't assume that they all point to the same file.
struct stat stat_buf = {};
struct stat lstat_buf = {};
auto rc = stat("/proc/self/fd/0", &stat_buf);
EXPECT_EQ(rc, 0);
rc = lstat("/proc/self/fd/0", &lstat_buf);
EXPECT_EQ(rc, 0);
EXPECT_NE(0, memcmp(&stat_buf, &lstat_buf, sizeof(struct stat)));
// Read the symlink value for stdin, stdout and stderr
auto link_length = readlink("/proc/self/fd/0", expected_link, sizeof(expected_link));
expected_link[link_length] = '\0';
stat_buf = {};
lstat_buf = {};
rc = stat("/proc/self/fd/1", &stat_buf);
EXPECT_EQ(rc, 0);
rc = lstat("/proc/self/fd/1", &lstat_buf);
EXPECT_EQ(rc, 0);
EXPECT_NE(0, memcmp(&stat_buf, &lstat_buf, sizeof(struct stat)));
link_length = readlink("/proc/self/fd/1", buf, sizeof(buf));
buf[link_length] = '\0';
EXPECT_EQ(0, strcmp(buf, expected_link));
link_length = readlink("/proc/self/fd/2", buf, sizeof(buf));
buf[link_length] = '\0';
EXPECT_EQ(0, strcmp(buf, expected_link));
stat_buf = {};
lstat_buf = {};
rc = stat("/proc/self/fd/2", &stat_buf);
EXPECT_EQ(rc, 0);
rc = lstat("/proc/self/fd/2", &lstat_buf);
EXPECT_EQ(rc, 0);
EXPECT_NE(0, memcmp(&stat_buf, &lstat_buf, sizeof(struct stat)));
// Create a new file descriptor that is a dup of 0 with various big values in order to reproduce issue #7820.
// We should get the same link value for each fd that was duplicated.
char expected_link[MAXPATHLEN];
char buf[MAXPATHLEN];
// Read the symlink for stdin, stdout and stderr
auto link_length = readlink("/proc/self/fd/0", expected_link, sizeof(expected_link));
expected_link[link_length] = '\0';
// 255 is the first broken file descriptor that was discovered and might be used by other software (e.g. bash)
auto new_fd = dup2(0, 255);