Commit 1e7ab6f6 authored by Christian Brauner's avatar Christian Brauner
Browse files

anon_inode: rework assertions 

Making anonymous inodes regular files comes with a lot of risk and
regression potential as evidenced by a recent hickup in io_uring. We're
better of continuing to not have them be regular files. Since we have
S_ANON_INODE we can port all of our assertions easily.

Link: https://lore.kernel.org/20250702-work-fixes-v1-1-ff76ea589e33@kernel.org


Fixes: cfd86ef7 ("anon_inode: use a proper mode internally")
Acked-by: default avatarJens Axboe <axboe@kernel.dk>
Cc: stable@kernel.org
Reported-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent d5cb81ba

fs/exec.c

+7 −2
Original line number Diff line number Diff line
@@ -114,6 +114,9 @@ static inline void put_binfmt(struct linux_binfmt * fmt) 


bool path_noexec(const struct path *path)

{

	/* If it's an anonymous inode make sure that we catch any shenanigans. */

	VFS_WARN_ON_ONCE(IS_ANON_FILE(d_inode(path->dentry)) &&

			 !(path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC));

	return (path->mnt->mnt_flags & MNT_NOEXEC) ||

	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);

}
@@ -781,13 +784,15 @@ static struct file *do_open_execat(int fd, struct filename *name, int flags) 
	if (IS_ERR(file))

		return file;



	if (path_noexec(&file->f_path))

		return ERR_PTR(-EACCES);



	/*

	 * In the past the regular type check was here. It moved to may_open() in

	 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is

	 * an invariant that all non-regular files error out before we get here.

	 */

	if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)) ||

	    path_noexec(&file->f_path))

	if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)))

		return ERR_PTR(-EACCES);



	err = exe_file_deny_write_access(file);

fs/libfs.c

+3 −5
Original line number Diff line number Diff line
@@ -1649,12 +1649,10 @@ struct inode *alloc_anon_inode(struct super_block *s) 
	 */

	inode->i_state = I_DIRTY;

	/*

	 * Historically anonymous inodes didn't have a type at all and

	 * userspace has come to rely on this. Internally they're just

	 * regular files but S_IFREG is masked off when reporting

	 * information to userspace.

	 * Historically anonymous inodes don't have a type at all and

	 * userspace has come to rely on this.

	 */

	inode->i_mode = S_IFREG | S_IRUSR | S_IWUSR;

	inode->i_mode = S_IRUSR | S_IWUSR;

	inode->i_uid = current_fsuid();

	inode->i_gid = current_fsgid();

	inode->i_flags |= S_PRIVATE | S_ANON_INODE;

fs/namei.c

+1 −1
Original line number Diff line number Diff line
@@ -3471,7 +3471,7 @@ static int may_open(struct mnt_idmap *idmap, const struct path *path, 
			return -EACCES;

		break;

	default:

		VFS_BUG_ON_INODE(1, inode);

		VFS_BUG_ON_INODE(!IS_ANON_FILE(inode), inode);

	}



	error = inode_permission(idmap, inode, MAY_OPEN | acc_mode);