linux/fs/proc
Linus Torvalds 0640113be2 vfs: Fix /proc/<tid>/fdinfo/<fd> file handling
Cyrill Gorcunov reports that I broke the fdinfo files with commit
30a08bf2d3 ("proc: move fd symlink i_mode calculations into
tid_fd_revalidate()"), and he's quite right.

The tid_fd_revalidate() function is not just used for the <tid>/fd
symlinks, it's also used for the <tid>/fdinfo/<fd> files, and the
permission model for those are different.

So do the dynamic symlink permission handling just for symlinks, making
the fdinfo files once more appear as the proper regular files they are.

Of course, Al Viro argued (probably correctly) that we shouldn't do the
symlink permission games at all, and make the symlinks always just be
the normal 'lrwxrwxrwx'.  That would have avoided this issue too, but
since somebody noticed that the permissions had changed (which was the
reason for that original commit 30a08bf2d3 in the first place), people
do apparently use this feature.

[ Basically, you can use the symlink permission data as a cheap "fdinfo"
  replacement, since you see whether the file is open for reading and/or
  writing by just looking at st_mode of the symlink.  So the feature
  does make sense, even if the pain it has caused means we probably
  shouldn't have done it to begin with. ]

Reported-and-tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-04 11:00:45 -07:00
..
array.c c/r: procfs: add arg_start/end, env_start/end and exit_code members to /proc/$pid/stat 2012-05-31 17:49:32 -07:00
base.c vfs: Fix /proc/<tid>/fdinfo/<fd> file handling 2012-06-04 11:00:45 -07:00
cmdline.c proc: switch /proc/cmdline to seq_file 2008-10-23 14:29:04 +04:00
consoles.c console: rename acquire/release_console_sem() to console_lock/unlock() 2011-01-26 10:50:06 +10:00
cpuinfo.c proc: move /proc/cpuinfo code to fs/proc/cpuinfo.c 2008-10-23 15:05:11 +04:00
devices.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
generic.c switch procfs to umode_t use 2012-01-03 22:54:56 -05:00
inode.c avoid iput() from flusher thread 2012-05-28 09:54:45 -07:00
internal.h fs, proc: introduce /proc/<pid>/task/<tid>/children entry 2012-05-31 17:49:32 -07:00
interrupts.c proc: move /proc/interrupts boilerplate code to fs/proc/interrupts.c 2008-10-23 15:15:46 +04:00
Kconfig kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
kcore.c fs/proc/kcore.c: make get_sparsemem_vmemmap_info() static 2012-03-23 16:58:42 -07:00
kmsg.c procfs: Use generic_file_llseek in /proc/kmsg 2010-04-09 16:35:41 +02:00
loadavg.c sched, timers: cleanup avenrun users 2009-05-15 15:32:45 +02:00
Makefile ns: proc files for namespace naming policy. 2011-05-10 14:31:44 -07:00
meminfo.c fs/proc/meminfo.c: fix compilation error 2011-12-09 07:50:28 -08:00
mmu.c
namespaces.c fs/proc/namespaces.c: prevent crash when ns_entries[] is empty 2012-03-28 17:14:37 -07:00
nommu.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
page.c pagemap: export KPF_THP 2012-03-21 17:54:57 -07:00
proc_devtree.c of/flattree: Drop an uninteresting message to pr_debug level 2011-03-02 13:45:18 -07:00
proc_net.c switch procfs to umode_t use 2012-01-03 22:54:56 -05:00
proc_sysctl.c userns: Convert sysctl permission checks to use kuid and kgids. 2012-05-15 14:59:28 -07:00
proc_tty.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
root.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2012-05-23 17:42:39 -07:00
softirqs.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
stat.c proc: stats: Use arch_idle_time for idle and iowait times if available 2012-03-30 15:43:33 +02:00
task_mmu.c proc/smaps: show amount of nonlinear ptes in vma 2012-05-31 17:49:29 -07:00
task_nommu.c proc: remove mm_for_maps() 2012-05-31 17:49:28 -07:00
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 proc: switch /proc/version to seq_file 2008-10-23 14:19:58 +04:00
vmcore.c fadump: Introduce cleanup routine to invalidate /proc/vmcore. 2012-02-23 10:50:02 +11:00