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Merge pull request #21079 from poettering/fd-reopen-directory-tweak

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fd-util: when re-opening a directory with fd_reopen() go via openat(……
This commit is contained in:
Lennart Poettering 2021-10-22 17:41:17 +02:00 committed by GitHub
commit a972ab0f25
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2 changed files with 112 additions and 3 deletions
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19
src/basic/fd-util.c
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@ -645,7 +645,7 @@ finish:
}
int fd_reopen(int fd, int flags) {
int new_fd;
int new_fd, r;
/* Reopens the specified fd with new flags. This is useful for convert an O_PATH fd into a regular one, or to
* turn O_RDWR fds into O_RDONLY fds.
@ -654,15 +654,28 @@ int fd_reopen(int fd, int flags) {
*
* This implicitly resets the file read index to 0. */
if (FLAGS_SET(flags, O_DIRECTORY)) {
/* If we shall reopen the fd as directory we can just go via "." and thus bypass the whole
* magic /proc/ directory, and make ourselves independent of that being mounted. */
new_fd = openat(fd, ".", flags);
if (new_fd < 0)
return -errno;
return new_fd;
}
new_fd = open(FORMAT_PROC_FD_PATH(fd), flags);
if (new_fd < 0) {
if (errno != ENOENT)
return -errno;
if (proc_mounted() == 0)
r = proc_mounted();
if (r == 0)
return -ENOSYS; /* if we have no /proc/, the concept is not implementable */
return -ENOENT;
return r > 0 ? -EBADF : -ENOENT; /* If /proc/ is definitely around then this means the fd is
* not valid, otherwise let's propagate the original
* error */
}
return new_fd;

96
src/test/test-fd-util.c
View File

@ -286,6 +286,101 @@ static void test_format_proc_fd_path(void) {
assert_se(streq_ptr(FORMAT_PROC_FD_PATH(2147483647), "/proc/self/fd/2147483647"));
}
static void test_fd_reopen(void) {
_cleanup_close_ int fd1 = -1, fd2 = -1;
struct stat st1, st2;
int fl;
/* Test this with a directory */
fd1 = open("/proc", O_DIRECTORY|O_PATH|O_CLOEXEC);
assert_se(fd1 >= 0);
assert_se(fstat(fd1, &st1) >= 0);
assert_se(S_ISDIR(st1.st_mode));
fl = fcntl(fd1, F_GETFL);
assert_se(fl >= 0);
assert_se(FLAGS_SET(fl, O_DIRECTORY));
assert_se(FLAGS_SET(fl, O_PATH));
fd2 = fd_reopen(fd1, O_RDONLY|O_DIRECTORY|O_CLOEXEC); /* drop the O_PATH */
assert_se(fd2 >= 0);
assert_se(fstat(fd2, &st2) >= 0);
assert_se(S_ISDIR(st2.st_mode));
assert_se(st1.st_ino == st2.st_ino);
assert_se(st1.st_rdev == st2.st_rdev);
fl = fcntl(fd2, F_GETFL);
assert_se(fl >= 0);
assert_se(FLAGS_SET(fl, O_DIRECTORY));
assert_se(!FLAGS_SET(fl, O_PATH));
safe_close(fd1);
fd1 = fd_reopen(fd2, O_DIRECTORY|O_PATH|O_CLOEXEC); /* reacquire the O_PATH */
assert_se(fd1 >= 0);
assert_se(fstat(fd1, &st1) >= 0);
assert_se(S_ISDIR(st1.st_mode));
assert_se(st1.st_ino == st2.st_ino);
assert_se(st1.st_rdev == st2.st_rdev);
fl = fcntl(fd1, F_GETFL);
assert_se(fl >= 0);
assert_se(FLAGS_SET(fl, O_DIRECTORY));
assert_se(FLAGS_SET(fl, O_PATH));
safe_close(fd1);
/* And now, test this with a file. */
fd1 = open("/proc/version", O_PATH|O_CLOEXEC);
assert_se(fd1 >= 0);
assert_se(fstat(fd1, &st1) >= 0);
assert_se(S_ISREG(st1.st_mode));
fl = fcntl(fd1, F_GETFL);
assert_se(fl >= 0);
assert_se(!FLAGS_SET(fl, O_DIRECTORY));
assert_se(FLAGS_SET(fl, O_PATH));
assert_se(fd_reopen(fd1, O_RDONLY|O_DIRECTORY|O_CLOEXEC) == -ENOTDIR);
fd2 = fd_reopen(fd1, O_RDONLY|O_CLOEXEC); /* drop the O_PATH */
assert_se(fd2 >= 0);
assert_se(fstat(fd2, &st2) >= 0);
assert_se(S_ISREG(st2.st_mode));
assert_se(st1.st_ino == st2.st_ino);
assert_se(st1.st_rdev == st2.st_rdev);
fl = fcntl(fd2, F_GETFL);
assert_se(fl >= 0);
assert_se(!FLAGS_SET(fl, O_DIRECTORY));
assert_se(!FLAGS_SET(fl, O_PATH));
safe_close(fd1);
assert_se(fd_reopen(fd2, O_DIRECTORY|O_PATH|O_CLOEXEC) == -ENOTDIR);
fd1 = fd_reopen(fd2, O_PATH|O_CLOEXEC); /* reacquire the O_PATH */
assert_se(fd1 >= 0);
assert_se(fstat(fd1, &st1) >= 0);
assert_se(S_ISREG(st1.st_mode));
assert_se(st1.st_ino == st2.st_ino);
assert_se(st1.st_rdev == st2.st_rdev);
fl = fcntl(fd1, F_GETFL);
assert_se(fl >= 0);
assert_se(!FLAGS_SET(fl, O_DIRECTORY));
assert_se(FLAGS_SET(fl, O_PATH));
/* Also check the right error is generated if the fd is already closed */
safe_close(fd1);
assert_se(fd_reopen(fd1, O_RDONLY|O_CLOEXEC) == -EBADF);
fd1 = -1;
}
int main(int argc, char *argv[]) {
test_setup_logging(LOG_DEBUG);
@ -299,6 +394,7 @@ int main(int argc, char *argv[]) {
test_read_nr_open();
test_close_all_fds();
test_format_proc_fd_path();
test_fd_reopen();
return 0;
}