To get an operable version of an O_PATH file descriptors, it is possible to use openat(fd, ".", O_DIRECTORY) for directories, but other files currently require going through open("/proc//fd/") which depends on a functioning procfs. This patch adds the O_EMPTY_PATH flag to openat and openat2. If passed LOOKUP_EMPTY is set at path resolve time. Signed-off-by: Jori Koolstra --- fs/fcntl.c | 2 +- fs/open.c | 6 ++++-- include/linux/fcntl.h | 2 +- include/uapi/asm-generic/fcntl.h | 4 ++++ 4 files changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/fcntl.c b/fs/fcntl.c index f93dbca08435..62ab4ad2b6f5 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -1169,7 +1169,7 @@ static int __init fcntl_init(void) * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY * is defined as O_NONBLOCK on some platforms and not on others. */ - BUILD_BUG_ON(20 - 1 /* for O_RDONLY being 0 */ != + BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) | __FMODE_EXEC)); diff --git a/fs/open.c b/fs/open.c index 91f1139591ab..32865822ca1c 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1160,7 +1160,7 @@ struct file *kernel_file_open(const struct path *path, int flags, EXPORT_SYMBOL_GPL(kernel_file_open); #define WILL_CREATE(flags) (flags & (O_CREAT | __O_TMPFILE)) -#define O_PATH_FLAGS (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC) +#define O_PATH_FLAGS (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC | O_EMPTY_PATH) inline struct open_how build_open_how(int flags, umode_t mode) { @@ -1277,6 +1277,8 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op) } } + if (flags & O_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; if (flags & O_DIRECTORY) lookup_flags |= LOOKUP_DIRECTORY; if (!(flags & O_NOFOLLOW)) @@ -1362,7 +1364,7 @@ static int do_sys_openat2(int dfd, const char __user *filename, if (unlikely(err)) return err; - CLASS(filename, name)(filename); + CLASS(filename_flags, name)(filename, op.lookup_flags); return FD_ADD(how->flags, do_file_open(dfd, name, &op)); } diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index a332e79b3207..ce742f67bf60 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -10,7 +10,7 @@ (O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \ O_APPEND | O_NDELAY | O_NONBLOCK | __O_SYNC | O_DSYNC | \ FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \ - O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE) + O_NOATIME | O_CLOEXEC | O_PATH | O_EMPTY_PATH | __O_TMPFILE) /* List of all valid flags for the how->resolve argument: */ #define VALID_RESOLVE_FLAGS \ diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index 613475285643..8e4e796ad212 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -88,6 +88,10 @@ #define __O_TMPFILE 020000000 #endif +#ifndef O_EMPTY_PATH +#define O_EMPTY_PATH 0100000000 +#endif + /* a horrid kludge trying to make sure that this will fail on old kernels */ #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) -- 2.53.0