kernel.git/fs/namei.c, branch linux-3.19.y

RCU pathwalk breakage when running into a symlink overmounting something

2015-05-06T20:02:02Z

commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 upstream. Calling unlazy_walk() in walk_component() and do_last() when we find a symlink that needs to be followed doesn't acquire a reference to vfsmount. That's fine when the symlink is on the same vfsmount as the parent directory (which is almost always the case), but it's not always true - one _can_ manage to bind a symlink on top of something. And in such cases we end up with excessive mntput(). Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2014-12-16T23:53:03Z

Pull vfs pile #2 from Al Viro: "Next pile (and there'll be one or two more). The large piece in this one is getting rid of /proc/*/ns/* weirdness; among other things, it allows to (finally) make nameidata completely opaque outside of fs/namei.c, making for easier further cleanups in there" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: coda_venus_readdir(): use file_inode() fs/namei.c: fold link_path_walk() call into path_init() path_init(): don't bother with LOOKUP_PARENT in argument fs/namei.c: new helper (path_cleanup()) path_init(): store the "base" pointer to file in nameidata itself make default ->i_fop have ->open() fail with ENXIO make nameidata completely opaque outside of fs/namei.c kill proc_ns completely take the targets of /proc/*/ns/* symlinks to separate fs bury struct proc_ns in fs/proc copy address of proc_ns_ops into ns_common new helpers: ns_alloc_inum/ns_free_inum make proc_ns_operations work with struct ns_common * instead of void * switch the rest of proc_ns_operations to working with &...->ns netns: switch ->get()/->put()/->install()/->inum() to working with &net->ns make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns common object embedded into various struct ....ns

syscalls: implement execveat() system call

2014-12-13T20:42:51Z

This patchset adds execveat(2) for x86, and is derived from Meredydd Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528). The primary aim of adding an execveat syscall is to allow an implementation of fexecve(3) that does not rely on the /proc filesystem, at least for executables (rather than scripts). The current glibc version of fexecve(3) is implemented via /proc, which causes problems in sandboxed or otherwise restricted environments. Given the desire for a /proc-free fexecve() implementation, HPA suggested (https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be an appropriate generalization. Also, having a new syscall means that it can take a flags argument without back-compatibility concerns. The current implementation just defines the AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be added in future -- for example, flags for new namespaces (as suggested at https://lkml.org/lkml/2006/7/11/474). Related history: - https://lkml.org/lkml/2006/12/27/123 is an example of someone realizing that fexecve() is likely to fail in a chroot environment. - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered documenting the /proc requirement of fexecve(3) in its manpage, to "prevent other people from wasting their time". - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a problem where a process that did setuid() could not fexecve() because it no longer had access to /proc/self/fd; this has since been fixed. This patch (of 4): Add a new execveat(2) system call. execveat() is to execve() as openat() is to open(): it takes a file descriptor that refers to a directory, and resolves the filename relative to that. In addition, if the filename is empty and AT_EMPTY_PATH is specified, execveat() executes the file to which the file descriptor refers. This replicates the functionality of fexecve(), which is a system call in other UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/" (and so relies on /proc being mounted). The filename fed to the executed program as argv[0] (or the name of the script fed to a script interpreter) will be of the form "/dev/fd/" (for an empty filename) or "/dev/fd//", effectively reflecting how the executable was found. This does however mean that execution of a script in a /proc-less environment won't work; also, script execution via an O_CLOEXEC file descriptor fails (as the file will not be accessible after exec). Based on patches by Meredydd Luff. Signed-off-by: David Drysdale Cc: Meredydd Luff Cc: Shuah Khan Cc: "Eric W. Biederman" Cc: Andy Lutomirski Cc: Alexander Viro Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Kees Cook Cc: Arnd Bergmann Cc: Rich Felker Cc: Christoph Hellwig Cc: Michael Kerrisk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs/namei.c: fold link_path_walk() call into path_init()

2014-12-11T21:27:57Z

Signed-off-by: Al Viro

path_init(): don't bother with LOOKUP_PARENT in argument

2014-12-11T21:27:57Z

Signed-off-by: Al Viro

fs/namei.c: new helper (path_cleanup())

2014-12-11T21:27:57Z

All callers of path_init() proceed to do the identical cleanup when they are done with nameidata. Don't open-code it... Signed-off-by: Al Viro

path_init(): store the "base" pointer to file in nameidata itself

2014-12-11T21:27:57Z

Signed-off-by: Al Viro

make nameidata completely opaque outside of fs/namei.c

2014-12-11T02:32:13Z

Signed-off-by: Al Viro

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2014-11-02T18:28:43Z

Pull VFS fixes from Al Viro: "A bunch of assorted fixes, most of them followups to overlayfs merge" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: ovl: initialize ->is_cursor Return short read or 0 at end of a raw device, not EIO isofs: don't bother with ->d_op for normal case isofs_cmp(): we'll never see a dentry for . or .. overlayfs: fix lockdep misannotation ovl: fix check for cursor overlayfs: barriers for opening upper-layer directory rcu: Provide counterpart to rcu_dereference() for non-RCU situations staging: android: logger: Fix log corruption regression

fs: allow open(dir, O_TMPFILE|..., 0) with mode 0

2014-10-30T22:50:13Z

The man page for open(2) indicates that when O_CREAT is specified, the 'mode' argument applies only to future accesses to the file: Note that this mode applies only to future accesses of the newly created file; the open() call that creates a read-only file may well return a read/write file descriptor. The man page for open(2) implies that 'mode' is treated identically by O_CREAT and O_TMPFILE. O_TMPFILE, however, behaves differently: int fd = open("/tmp", O_TMPFILE | O_RDWR, 0); assert(fd == -1); assert(errno == EACCES); int fd = open("/tmp", O_TMPFILE | O_RDWR, 0600); assert(fd > 0); For O_CREAT, do_last() sets acc_mode to MAY_OPEN only: if (*opened & FILE_CREATED) { /* Don't check for write permission, don't truncate */ open_flag &= ~O_TRUNC; will_truncate = false; acc_mode = MAY_OPEN; path_to_nameidata(path, nd); goto finish_open_created; } But for O_TMPFILE, do_tmpfile() passes the full op->acc_mode to may_open(). This patch lines up the behavior of O_TMPFILE with O_CREAT. After the inode is created, may_open() is called with acc_mode = MAY_OPEN, in do_tmpfile(). A different, but related glibc bug revealed the discrepancy: https://sourceware.org/bugzilla/show_bug.cgi?id=17523 The glibc lazily loads the 'mode' argument of open() and openat() using va_arg() only if O_CREAT is present in 'flags' (to support both the 2 argument and the 3 argument forms of open; same idea for openat()). However, the glibc ignores the 'mode' argument if O_TMPFILE is in 'flags'. On x86_64, for open(), it magically works anyway, as 'mode' is in RDX when entering open(), and is still in RDX on SYSCALL, which is where the kernel looks for the 3rd argument of a syscall. But openat() is not quite so lucky: 'mode' is in RCX when entering the glibc wrapper for openat(), while the kernel looks for the 4th argument of a syscall in R10. Indeed, the syscall calling convention differs from the regular calling convention in this respect on x86_64. So the kernel sees mode = 0 when trying to use glibc openat() with O_TMPFILE, and fails with EACCES. Signed-off-by: Eric Rannaud Acked-by: Andy Lutomirski Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds