Add additional RESOLVE_* flags to correspond to AT_* flags that aren't
currently implemented:
RESOLVE_NO_TRAILING_SYMLINKS for AT_SYMLINK_NOFOLLOW
RESOLVE_NO_TRAILING_AUTOMOUNTS for AT_NO_AUTOMOUNT
RESOLVE_EMPTY_PATH for AT_EMPTY_PATH
This is necessary for fsinfo() to use RESOLVE_* flags instead of AT_* flags
if the latter are to be considered deprecated for new system calls.
Also make openat2() handle RESOLVE_NO_TRAILING_SYMLINKS.
Automounting is currently forced by doing an open(), so adding support to
openat2() for RESOLVE_NO_TRAILING_AUTOMOUNTS is not trivial.
Reported-by: Stefan Metzmacher <metze@xxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Aleksa Sarai <cyphar@xxxxxxxxxx>
---
fs/open.c | 8 +++++---
include/linux/fcntl.h | 3 ++-
include/uapi/linux/openat2.h | 8 +++++++-
3 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/fs/open.c b/fs/open.c
index 0788b3715731..7c38a7605c21 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -977,7 +977,7 @@ inline struct open_how build_open_how(int flags, umode_t mode)
inline int build_open_flags(const struct open_how *how, struct open_flags *op)
{
int flags = how->flags;
- int lookup_flags = 0;
+ int lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
int acc_mode = ACC_MODE(flags);
/* Must never be set by userspace */
@@ -1055,8 +1055,8 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
if (flags & O_DIRECTORY)
lookup_flags |= LOOKUP_DIRECTORY;
- if (!(flags & O_NOFOLLOW))
- lookup_flags |= LOOKUP_FOLLOW;
+ if (flags & O_NOFOLLOW)
+ lookup_flags &= ~LOOKUP_FOLLOW;
if (how->resolve & RESOLVE_NO_XDEV)
lookup_flags |= LOOKUP_NO_XDEV;
@@ -1068,6 +1068,8 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
lookup_flags |= LOOKUP_BENEATH;
if (how->resolve & RESOLVE_IN_ROOT)
lookup_flags |= LOOKUP_IN_ROOT;
+ if (how->resolve & RESOLVE_NO_TRAILING_SYMLINKS)
+ lookup_flags &= ~LOOKUP_FOLLOW;
op->lookup_flags = lookup_flags;
return 0;
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 7bcdcf4f6ab2..eacf17a8ca34 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -19,7 +19,8 @@
/* List of all valid flags for the how->resolve argument: */
#define VALID_RESOLVE_FLAGS \
(RESOLVE_NO_XDEV | RESOLVE_NO_MAGICLINKS | RESOLVE_NO_SYMLINKS | \
- RESOLVE_BENEATH | RESOLVE_IN_ROOT)
+ RESOLVE_BENEATH | RESOLVE_IN_ROOT | RESOLVE_NO_TRAILING_SYMLINKS | \
+ RESOLVE_NO_TRAILING_AUTOMOUNTS | RESOLVE_EMPTY_PATH)
/* List of all open_how "versions". */
#define OPEN_HOW_SIZE_VER0 24 /* sizeof first published struct */
diff --git a/include/uapi/linux/openat2.h b/include/uapi/linux/openat2.h
index 58b1eb711360..2647a108f116 100644
--- a/include/uapi/linux/openat2.h
+++ b/include/uapi/linux/openat2.h
@@ -22,7 +22,10 @@ struct open_how {
__u64 resolve;
};
-/* how->resolve flags for openat2(2). */
+/*
+ * Path resolution paths to replace AT_* paths in all new syscalls that would
+ * use them.
+ */
#define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
(includes bind-mounts). */
#define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
@@ -35,5 +38,8 @@ struct open_how {
#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
be scoped inside the dirfd
(similar to chroot(2)). */
+#define RESOLVE_NO_TRAILING_SYMLINKS 0x20 /* Don't follow trailing symlinks in the path */
+#define RESOLVE_NO_TRAILING_AUTOMOUNTS 0x40 /* Don't follow trailing automounts in the path */
+#define RESOLVE_EMPTY_PATH 0x80 /* Permit a path of "" to indicate the dfd exactly */
#endif /* _UAPI_LINUX_OPENAT2_H */
