67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <unistd.h>
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#include "errno-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "macro.h"
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#include "memory-util.h"
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#include "parse-util.h"
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#include "path-util.h"
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#include "pidfd-util.h"
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#include "string-util.h"
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int pidfd_get_pid(int fd, pid_t *ret) {
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char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
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_cleanup_free_ char *fdinfo = NULL;
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int r;
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/* Converts a pidfd into a pid. Well known errors:
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*
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* -EBADF → fd invalid
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* -ENOSYS → /proc/ not mounted
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* -ENOTTY → fd valid, but not a pidfd
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* -EREMOTE → fd valid, but pid is in another namespace we cannot translate to the local one
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* -ESRCH → fd valid, but process is already reaped
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*/
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assert(fd >= 0);
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xsprintf(path, "/proc/self/fdinfo/%i", fd);
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r = read_full_virtual_file(path, &fdinfo, NULL);
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if (r == -ENOENT)
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return proc_fd_enoent_errno();
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if (r < 0)
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return r;
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char *p = find_line_startswith(fdinfo, "Pid:");
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if (!p)
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return -ENOTTY; /* not a pidfd? */
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p = skip_leading_chars(p, /* bad = */ NULL);
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p[strcspn(p, WHITESPACE)] = 0;
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if (streq(p, "0"))
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return -EREMOTE; /* PID is in foreign PID namespace? */
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if (streq(p, "-1"))
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return -ESRCH; /* refers to reaped process? */
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return parse_pid(p, ret);
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}
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int pidfd_verify_pid(int pidfd, pid_t pid) {
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pid_t current_pid;
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int r;
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assert(pidfd >= 0);
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assert(pid > 0);
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r = pidfd_get_pid(pidfd, ¤t_pid);
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if (r < 0)
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return r;
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return current_pid != pid ? -ESRCH : 0;
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}
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