diff options
Diffstat (limited to 'src/basic/chattr-util.c')
| -rw-r--r-- | src/basic/chattr-util.c | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/src/basic/chattr-util.c b/src/basic/chattr-util.c new file mode 100644 index 0000000..eddde13 --- /dev/null +++ b/src/basic/chattr-util.c @@ -0,0 +1,162 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <errno.h> +#include <fcntl.h> +#include <sys/ioctl.h> +#include <sys/stat.h> +#include <linux/fs.h> + +#include "chattr-util.h" +#include "errno-util.h" +#include "fd-util.h" +#include "macro.h" +#include "string-util.h" + +int chattr_full(const char *path, + int fd, + unsigned value, + unsigned mask, + unsigned *ret_previous, + unsigned *ret_final, + ChattrApplyFlags flags) { + + _cleanup_close_ int fd_will_close = -1; + unsigned old_attr, new_attr; + int set_flags_errno = 0; + struct stat st; + + assert(path || fd >= 0); + + if (fd < 0) { + fd = fd_will_close = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); + if (fd < 0) + return -errno; + } + + if (fstat(fd, &st) < 0) + return -errno; + + /* Explicitly check whether this is a regular file or directory. If it is anything else (such + * as a device node or fifo), then the ioctl will not hit the file systems but possibly + * drivers, where the ioctl might have different effects. Notably, DRM is using the same + * ioctl() number. */ + + if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode)) + return -ENOTTY; + + if (mask == 0 && !ret_previous && !ret_final) + return 0; + + if (ioctl(fd, FS_IOC_GETFLAGS, &old_attr) < 0) + return -errno; + + new_attr = (old_attr & ~mask) | (value & mask); + if (new_attr == old_attr) { + if (ret_previous) + *ret_previous = old_attr; + if (ret_final) + *ret_final = old_attr; + return 0; + } + + if (ioctl(fd, FS_IOC_SETFLAGS, &new_attr) >= 0) { + unsigned attr; + + /* Some filesystems (BTRFS) silently fail when a flag cannot be set. Let's make sure our + * changes actually went through by querying the flags again and verifying they're equal to + * the flags we tried to configure. */ + + if (ioctl(fd, FS_IOC_GETFLAGS, &attr) < 0) + return -errno; + + if (new_attr == attr) { + if (ret_previous) + *ret_previous = old_attr; + if (ret_final) + *ret_final = new_attr; + return 1; + } + + /* Trigger the fallback logic. */ + errno = EINVAL; + } + + if ((errno != EINVAL && !ERRNO_IS_NOT_SUPPORTED(errno)) || + !FLAGS_SET(flags, CHATTR_FALLBACK_BITWISE)) + return -errno; + + /* When -EINVAL is returned, we assume that incompatible attributes are simultaneously + * specified. E.g., compress(c) and nocow(C) attributes cannot be set to files on btrfs. + * As a fallback, let's try to set attributes one by one. + * + * Also, when we get EOPNOTSUPP (or a similar error code) we assume a flag might just not be + * supported, and we can ignore it too */ + + unsigned current_attr = old_attr; + for (unsigned i = 0; i < sizeof(unsigned) * 8; i++) { + unsigned new_one, mask_one = 1u << i; + + if (!FLAGS_SET(mask, mask_one)) + continue; + + new_one = UPDATE_FLAG(current_attr, mask_one, FLAGS_SET(value, mask_one)); + if (new_one == current_attr) + continue; + + if (ioctl(fd, FS_IOC_SETFLAGS, &new_one) < 0) { + if (errno != EINVAL && !ERRNO_IS_NOT_SUPPORTED(errno)) + return -errno; + + log_full_errno(FLAGS_SET(flags, CHATTR_WARN_UNSUPPORTED_FLAGS) ? LOG_WARNING : LOG_DEBUG, + errno, + "Unable to set file attribute 0x%x on %s, ignoring: %m", mask_one, strna(path)); + + /* Ensures that we record whether only EOPNOTSUPP&friends are encountered, or if a more serious + * error (thus worth logging at a different level, etc) was seen too. */ + if (set_flags_errno == 0 || !ERRNO_IS_NOT_SUPPORTED(errno)) + set_flags_errno = -errno; + + continue; + } + + if (ioctl(fd, FS_IOC_GETFLAGS, ¤t_attr) < 0) + return -errno; + } + + if (ret_previous) + *ret_previous = old_attr; + if (ret_final) + *ret_final = current_attr; + + /* -ENOANO indicates that some attributes cannot be set. ERRNO_IS_NOT_SUPPORTED indicates that all + * encountered failures were due to flags not supported by the FS, so return a specific error in + * that case, so callers can handle it properly (e.g.: tmpfiles.d can use debug level logging). */ + return current_attr == new_attr ? 1 : ERRNO_IS_NOT_SUPPORTED(set_flags_errno) ? set_flags_errno : -ENOANO; +} + +int read_attr_fd(int fd, unsigned *ret) { + struct stat st; + + assert(fd >= 0); + + if (fstat(fd, &st) < 0) + return -errno; + + if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode)) + return -ENOTTY; + + return RET_NERRNO(ioctl(fd, FS_IOC_GETFLAGS, ret)); +} + +int read_attr_path(const char *p, unsigned *ret) { + _cleanup_close_ int fd = -1; + + assert(p); + assert(ret); + + fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); + if (fd < 0) + return -errno; + + return read_attr_fd(fd, ret); +} |