linux/fs/proc
Linus Torvalds 51f0885e54 vfs,proc: guarantee unique inodes in /proc
Dave Jones found another /proc issue with his Trinity tool: thanks to
the namespace model, we can have multiple /proc dentries that point to
the same inode, aliasing directories in /proc/<pid>/net/ for example.

This ends up being a total disaster, because it acts like hardlinked
directories, and causes locking problems.  We rely on the topological
sort of the inodes pointed to by dentries, and if we have aliased
directories, that odering becomes unreliable.

In short: don't do this.  Multiple dentries with the same (directory)
inode is just a bad idea, and the namespace code should never have
exposed things this way.  But we're kind of stuck with it.

This solves things by just always allocating a new inode during /proc
dentry lookup, instead of using "iget_locked()" to look up existing
inodes by superblock and number.  That actually simplies the code a bit,
at the cost of potentially doing more inode [de]allocations.

That said, the inode lookup wasn't free either (and did a lot of locking
of inodes), so it is probably not that noticeable.  We could easily keep
the old lookup model for non-directory entries, but rather than try to
be excessively clever this just implements the minimal and simplest
workaround for the problem.

Reported-and-tested-by: Dave Jones <davej@redhat.com>
Analyzed-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-03-22 11:44:04 -07:00
..
array.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
base.c fs/proc: clean up printks 2013-02-27 19:10:11 -08:00
cmdline.c
consoles.c console: rename acquire/release_console_sem() to console_lock/unlock() 2011-01-26 10:50:06 +10:00
cpuinfo.c
devices.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
fd.c procfs: add ability to plug in auxiliary fdinfo providers 2012-12-17 17:15:27 -08:00
fd.h procfs: Move /proc/pid/fd[info] handling code to fd.[ch] 2012-09-26 21:10:01 -04:00
generic.c fs/proc: clean up printks 2013-02-27 19:10:11 -08:00
inode.c vfs,proc: guarantee unique inodes in /proc 2013-03-22 11:44:04 -07:00
internal.h coredump: remove redundant defines for dumpable states 2013-02-27 19:10:11 -08:00
interrupts.c
Kconfig kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
kcore.c fs/proc: clean up printks 2013-02-27 19:10:11 -08:00
kmsg.c procfs: Use generic_file_llseek in /proc/kmsg 2010-04-09 16:35:41 +02:00
loadavg.c
Makefile tty: Added a CONFIG_TTY option to allow removal of TTY 2013-01-18 16:15:27 -08:00
meminfo.c swap: make each swap partition have one address_space 2013-02-23 17:50:17 -08:00
mmu.c
namespaces.c proc: Use nd_jump_link in proc_ns_follow_link 2013-03-09 00:14:45 -08:00
nommu.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
page.c kpageflags: fix wrong KPF_THP on non-huge compound pages 2012-10-09 16:23:00 +09:00
proc_devtree.c fs/proc: clean up printks 2013-02-27 19:10:11 -08:00
proc_net.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
proc_sysctl.c fs/proc: clean up printks 2013-02-27 19:10:11 -08:00
proc_tty.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
root.c userns: Allow unprivilged mounts of proc and sysfs 2012-11-20 04:19:18 -08:00
self.c procfs: Use the proc generic infrastructure for proc/self. 2012-11-19 03:09:34 -08:00
softirqs.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
stat.c nohz: Fix idle ticks in cpu summary line of /proc/stat 2012-10-10 14:05:21 +02:00
task_mmu.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
task_nommu.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
uptime.c Merge branch 'sched/core' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into cputime-tip 2011-12-19 19:23:15 +01:00
version.c
vmcore.c fs/proc/vmcore.c: put if tests in the top of the while loop to reduce duplication 2013-02-27 19:10:11 -08:00