diff options
Diffstat (limited to 'lib/renameatu.c')
| -rw-r--r-- | lib/renameatu.c | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/lib/renameatu.c b/lib/renameatu.c new file mode 100644 index 0000000..939e589 --- /dev/null +++ b/lib/renameatu.c @@ -0,0 +1,254 @@ +/* Rename a file relative to open directories. + Copyright (C) 2009-2023 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* written by Eric Blake and Paul Eggert */ + +#include <config.h> + +#include "renameatu.h" + +#include <errno.h> +#include <stdio.h> +#include <sys/stat.h> +#include <unistd.h> + +#ifdef __linux__ +# include <sys/syscall.h> +#endif + +static int +errno_fail (int e) +{ + errno = e; + return -1; +} + +#if HAVE_RENAMEAT + +# include <stdlib.h> +# include <string.h> + +# include "dirname.h" +# include "openat.h" + +#else +# include "openat-priv.h" + +static int +rename_noreplace (char const *src, char const *dst) +{ + /* This has a race between the call to lstat and the call to rename. */ + struct stat st; + return (lstat (dst, &st) == 0 || errno == EOVERFLOW ? errno_fail (EEXIST) + : errno == ENOENT ? rename (src, dst) + : -1); +} +#endif + +#undef renameat + +#if HAVE_RENAMEAT + +/* Act like renameat (FD1, SRC, FD2, DST), except fail with EEXIST if + FLAGS is nonzero and it is easy to fail atomically if DST already exists. + This lets renameatu be atomic when it can be implemented in terms + of renameatx_np. */ +static int +renameat2ish (int fd1, char const *src, int fd2, char const *dst, + unsigned int flags) +{ +# ifdef RENAME_EXCL + if (flags) + { + int r = renameatx_np (fd1, src, fd2, dst, RENAME_EXCL); + if (r == 0 || errno != ENOTSUP) + return r; + } +# endif + + return renameat (fd1, src, fd2, dst); +} +#endif + +/* Rename FILE1, in the directory open on descriptor FD1, to FILE2, in + the directory open on descriptor FD2. If possible, do it without + changing the working directory. Otherwise, resort to using + save_cwd/fchdir, then rename/restore_cwd. If either the save_cwd or + the restore_cwd fails, then give a diagnostic and exit nonzero. + + Obey FLAGS when doing the renaming. If FLAGS is zero, this + function is equivalent to renameat (FD1, SRC, FD2, DST). + Otherwise, attempt to implement FLAGS even if the implementation is + not atomic; this differs from the GNU/Linux native renameat2, + which fails if it cannot guarantee atomicity. */ + +int +renameatu (int fd1, char const *src, int fd2, char const *dst, + unsigned int flags) +{ + int ret_val = -1; + int err = EINVAL; + +#ifdef HAVE_RENAMEAT2 + ret_val = renameat2 (fd1, src, fd2, dst, flags); + err = errno; +#elif defined SYS_renameat2 + ret_val = syscall (SYS_renameat2, fd1, src, fd2, dst, flags); + err = errno; +#endif + + if (! (ret_val < 0 && (err == EINVAL || err == ENOSYS || err == ENOTSUP))) + return ret_val; + +#if HAVE_RENAMEAT + { + size_t src_len; + size_t dst_len; + char *src_temp = (char *) src; + char *dst_temp = (char *) dst; + bool src_slash; + bool dst_slash; + int rename_errno = ENOTDIR; + struct stat src_st; + struct stat dst_st; + bool dst_found_nonexistent = false; + + switch (flags) + { + case 0: + break; + + case RENAME_NOREPLACE: + /* This has a race between the call to fstatat and the calls to + renameat below. This fstatat is needed even if RENAME_EXCL + is defined, because RENAME_EXCL is buggy on macOS 11.2: + renameatx_np (fd, "X", fd, "X", RENAME_EXCL) incorrectly + succeeds when X exists. */ + if (fstatat (fd2, dst, &dst_st, AT_SYMLINK_NOFOLLOW) == 0 + || errno == EOVERFLOW) + return errno_fail (EEXIST); + if (errno != ENOENT) + return -1; + dst_found_nonexistent = true; + break; + + default: + return errno_fail (ENOTSUP); + } + + /* Let strace see any ENOENT failure. */ + src_len = strlen (src); + dst_len = strlen (dst); + if (!src_len || !dst_len) + return renameat2ish (fd1, src, fd2, dst, flags); + + src_slash = src[src_len - 1] == '/'; + dst_slash = dst[dst_len - 1] == '/'; + if (!src_slash && !dst_slash) + return renameat2ish (fd1, src, fd2, dst, flags); + + /* Presence of a trailing slash requires directory semantics. If + the source does not exist, or if the destination cannot be turned + into a directory, give up now. Otherwise, strip trailing slashes + before calling rename. */ + if (fstatat (fd1, src, &src_st, AT_SYMLINK_NOFOLLOW)) + return -1; + if (dst_found_nonexistent) + { + if (!S_ISDIR (src_st.st_mode)) + return errno_fail (ENOENT); + } + else if (fstatat (fd2, dst, &dst_st, AT_SYMLINK_NOFOLLOW)) + { + if (errno != ENOENT || !S_ISDIR (src_st.st_mode)) + return -1; + } + else if (!S_ISDIR (dst_st.st_mode)) + return errno_fail (ENOTDIR); + else if (!S_ISDIR (src_st.st_mode)) + return errno_fail (EISDIR); + +# if RENAME_TRAILING_SLASH_SOURCE_BUG + /* See the lengthy comment in rename.c why Solaris 9 is forced to + GNU behavior, while Solaris 10 is left with POSIX behavior, + regarding symlinks with trailing slash. */ + ret_val = -1; + if (src_slash) + { + src_temp = strdup (src); + if (!src_temp) + { + /* Rather than rely on strdup-posix, we set errno ourselves. */ + rename_errno = ENOMEM; + goto out; + } + strip_trailing_slashes (src_temp); + if (fstatat (fd1, src_temp, &src_st, AT_SYMLINK_NOFOLLOW)) + { + rename_errno = errno; + goto out; + } + if (S_ISLNK (src_st.st_mode)) + goto out; + } + if (dst_slash) + { + dst_temp = strdup (dst); + if (!dst_temp) + { + rename_errno = ENOMEM; + goto out; + } + strip_trailing_slashes (dst_temp); + char readlink_buf[1]; + if (readlinkat (fd2, dst_temp, readlink_buf, sizeof readlink_buf) < 0) + { + if (errno != ENOENT && errno != EINVAL) + { + rename_errno = errno; + goto out; + } + } + else + goto out; + } +# endif /* RENAME_TRAILING_SLASH_SOURCE_BUG */ + + /* renameat does not honor trailing / on Solaris 10. Solve it in a + similar manner to rename. No need to worry about bugs not present + on Solaris, since all other systems either lack renameat or honor + trailing slash correctly. */ + + ret_val = renameat2ish (fd1, src_temp, fd2, dst_temp, flags); + rename_errno = errno; + goto out; + out: + if (src_temp != src) + free (src_temp); + if (dst_temp != dst) + free (dst_temp); + errno = rename_errno; + return ret_val; + } +#else /* !HAVE_RENAMEAT */ + + /* RENAME_NOREPLACE is the only flag currently supported. */ + if (flags & ~RENAME_NOREPLACE) + return errno_fail (ENOTSUP); + return at_func2 (fd1, src, fd2, dst, flags ? rename_noreplace : rename); + +#endif /* !HAVE_RENAMEAT */ +} |