Cited from commit message of original patch [1]:
One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission.
Also, generally all *at() syscalls operate on O_PATH fds, unlike f*() ones. Yet the O_PATH fds are rejected by *xattrat() syscalls in the final version merged into tree. Instead, let's switch things to CLASS(fd_raw).
Note that there's one side effect: f*xattr() starts to work with O_PATH fds too. It's not clear to me whether this is desirable (e.g. fstat() accepts O_PATH fds as an outlier).
[1] https://lore.kernel.org/all/20240426162042.191916-1-cgoettsche@seltendoof.de...
Fixes: 6140be90ec70 ("fs/xattr: add *at family syscalls") Signed-off-by: Mike Yuan me@yhndnzj.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: Christian Göttsche cgzones@googlemail.com Cc: Christian Brauner brauner@kernel.org Cc: stable@vger.kernel.org --- fs/xattr.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/xattr.c b/fs/xattr.c index 02bee149ad96..15df71e56187 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -704,7 +704,7 @@ static int path_setxattrat(int dfd, const char __user *pathname,
filename = getname_maybe_null(pathname, at_flags); if (!filename) { - CLASS(fd, f)(dfd); + CLASS(fd_raw, f)(dfd); if (fd_empty(f)) error = -EBADF; else @@ -848,7 +848,7 @@ static ssize_t path_getxattrat(int dfd, const char __user *pathname,
filename = getname_maybe_null(pathname, at_flags); if (!filename) { - CLASS(fd, f)(dfd); + CLASS(fd_raw, f)(dfd); if (fd_empty(f)) return -EBADF; return file_getxattr(fd_file(f), &ctx); @@ -978,7 +978,7 @@ static ssize_t path_listxattrat(int dfd, const char __user *pathname,
filename = getname_maybe_null(pathname, at_flags); if (!filename) { - CLASS(fd, f)(dfd); + CLASS(fd_raw, f)(dfd); if (fd_empty(f)) return -EBADF; return file_listxattr(fd_file(f), list, size); @@ -1079,7 +1079,7 @@ static int path_removexattrat(int dfd, const char __user *pathname,
filename = getname_maybe_null(pathname, at_flags); if (!filename) { - CLASS(fd, f)(dfd); + CLASS(fd_raw, f)(dfd); if (fd_empty(f)) return -EBADF; return file_removexattr(fd_file(f), &kname);
base-commit: a86bf2283d2c9769205407e2b54777c03d012939