linux-stable.git/fs/tracefs, branch v4.14.331

tracefs: Only clobber mode/uid/gid on remount if asked

2022-09-20T09:51:31+00:00

commit 47311db8e8f33011d90dee76b39c8886120cdda4 upstream.

Users may have explicitly configured their tracefs permissions; we
shouldn't overwrite those just because a second mount appeared.

Only clobber if the options were provided at mount time.

Note: the previous behavior was especially surprising in the presence of
automounted /sys/kernel/debug/tracing/.

Existing behavior:

  ## Pre-existing status: tracefs is 0755.
  # stat -c '%A' /sys/kernel/tracing/
  drwxr-xr-x

  ## (Re)trigger the automount.
  # umount /sys/kernel/debug/tracing
  # stat -c '%A' /sys/kernel/debug/tracing/.
  drwx------

  ## Unexpected: the automount changed mode for other mount instances.
  # stat -c '%A' /sys/kernel/tracing/
  drwx------

New behavior (after this change):

  ## Pre-existing status: tracefs is 0755.
  # stat -c '%A' /sys/kernel/tracing/
  drwxr-xr-x

  ## (Re)trigger the automount.
  # umount /sys/kernel/debug/tracing
  # stat -c '%A' /sys/kernel/debug/tracing/.
  drwxr-xr-x

  ## Expected: the automount does not change other mount instances.
  # stat -c '%A' /sys/kernel/tracing/
  drwxr-xr-x

Link: https://lkml.kernel.org/r/20220826174353.2.Iab6e5ea57963d6deca5311b27fb7226790d44406@changeid

Cc: stable@vger.kernel.org
Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system")
Signed-off-by: Brian Norris 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracefs: Set the group ownership in apply_options() not parse_options()

2022-03-02T10:33:58+00:00

commit 851e99ebeec3f4a672bb5010cf1ece095acee447 upstream.

Al Viro brought it to my attention that the dentries may not be filled
when the parse_options() is called, causing the call to set_gid() to
possibly crash. It should only be called if parse_options() succeeds
totally anyway.

He suggested the logical place to do the update is in apply_options().

Link: https://lore.kernel.org/all/20220225165219.737025658@goodmis.org/
Link: https://lkml.kernel.org/r/20220225153426.1c4cab6b@gandalf.local.home

Cc: stable@vger.kernel.org
Acked-by: Al Viro 
Reported-by: Al Viro 
Fixes: 48b27b6b5191 ("tracefs: Set all files to the same group ownership as the mount option")
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracefs: Set all files to the same group ownership as the mount option

2021-12-14T09:16:55+00:00

commit 48b27b6b5191e2e1f2798cd80877b6e4ef47c351 upstream.

As people have been asking to allow non-root processes to have access to
the tracefs directory, it was considered best to only allow groups to have
access to the directory, where it is easier to just set the tracefs file
system to a specific group (as other would be too dangerous), and that way
the admins could pick which processes would have access to tracefs.

Unfortunately, this broke tooling on Android that expected the other bit
to be set. For some special cases, for non-root tools to trace the system,
tracefs would be mounted and change the permissions of the top level
directory which gave access to all running tasks permission to the
tracing directory. Even though this would be dangerous to do in a
production environment, for testing environments this can be useful.

Now with the new changes to not allow other (which is still the proper
thing to do), it breaks the testing tooling. Now more code needs to be
loaded on the system to change ownership of the tracing directory.

The real solution is to have tracefs honor the gid=xxx option when
mounting. That is,

(tracing group tracing has value 1003)

 mount -t tracefs -o gid=1003 tracefs /sys/kernel/tracing

should have it that all files in the tracing directory should be of the
given group.

Copy the logic from d_walk() from dcache.c and simplify it for the mount
case of tracefs if gid is set. All the files in tracefs will be walked and
their group will be set to the value passed in.

Link: https://lkml.kernel.org/r/20211207171729.2a54e1b3@gandalf.local.home

Cc: Ingo Molnar 
Cc: Kees Cook 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: linux-fsdevel@vger.kernel.org
Cc: Al Viro 
Cc: Greg Kroah-Hartman 
Reported-by: Kalesh Singh 
Reported-by: Yabin Cui 
Fixes: 49d67e445742 ("tracefs: Have tracefs directories not set OTH permission bits by default")
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

tracefs: Have new files inherit the ownership of their parent

2021-12-14T09:16:54+00:00

commit ee7f3666995d8537dec17b1d35425f28877671a9 upstream.

If directories in tracefs have their ownership changed, then any new files
and directories that are created under those directories should inherit
the ownership of the director they are created in.

Link: https://lkml.kernel.org/r/20211208075720.4855d180@gandalf.local.home

Cc: Kees Cook 
Cc: Ingo Molnar 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Al Viro 
Cc: Greg Kroah-Hartman 
Cc: Yabin Cui 
Cc: Christian Brauner 
Cc: stable@vger.kernel.org
Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system")
Reported-by: Kalesh Singh 
Reported: https://lore.kernel.org/all/CAC_TJve8MMAv+H_NdLSJXZUSoxOEq2zB_pVaJ9p=7H6Bu3X76g@mail.gmail.com/
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

tracefs: Have tracefs directories not set OTH permission bits by default

2021-11-26T10:40:27+00:00

[ Upstream commit 49d67e445742bbcb03106b735b2ab39f6e5c56bc ]

The tracefs file system is by default mounted such that only root user can
access it. But there are legitimate reasons to create a group and allow
those added to the group to have access to tracing. By changing the
permissions of the tracefs mount point to allow access, it will allow
group access to the tracefs directory.

There should not be any real reason to allow all access to the tracefs
directory as it contains sensitive information. Have the default
permission of directories being created not have any OTH (other) bits set,
such that an admin that wants to give permission to a group has to first
disable all OTH bits in the file system.

Link: https://lkml.kernel.org/r/20210818153038.664127804@goodmis.org

Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Sasha Levin

VFS: Don't use save/replace_mount_options if not using generic_show_options

2017-07-06T07:31:46+00:00

btrfs, debugfs, reiserfs and tracefs call save_mount_options() and reiserfs
calls replace_mount_options(), but they then implement their own
->show_options() methods and don't touch s_options, rendering the saved
options unnecessary.  I'm trying to eliminate s_options to make it easier
to implement a context-based mount where the mount options can be passed
individually over a file descriptor.

Remove the calls to save/replace_mount_options() call in these cases.

Signed-off-by: David Howells 
cc: Chris Mason 
cc: Greg Kroah-Hartman 
cc: Steven Rostedt 
cc: linux-btrfs@vger.kernel.org
cc: reiserfs-devel@vger.kernel.org
Signed-off-by: Al Viro

fs: constify tree_descr arrays passed to simple_fill_super()

2017-04-27T03:54:06+00:00

simple_fill_super() is passed an array of tree_descr structures which
describe the files to create in the filesystem's root directory.  Since
these arrays are never modified intentionally, they should be 'const' so
that they are placed in .rodata and benefit from memory protection.
This patch updates the function signature and all users, and also
constifies tree_descr.name.

Signed-off-by: Eric Biggers 
Signed-off-by: Al Viro

fs: Replace CURRENT_TIME with current_time() for inode timestamps

2016-09-28T01:06:21+00:00

CURRENT_TIME macro is not appropriate for filesystems as it
doesn't use the right granularity for filesystem timestamps.
Use current_time() instead.

CURRENT_TIME is also not y2038 safe.

This is also in preparation for the patch that transitions
vfs timestamps to use 64 bit time and hence make them
y2038 safe. As part of the effort current_time() will be
extended to do range checks. Hence, it is necessary for all
file system timestamps to use current_time(). Also,
current_time() will be transitioned along with vfs to be
y2038 safe.

Note that whenever a single call to current_time() is used
to change timestamps in different inodes, it is because they
share the same time granularity.

Signed-off-by: Deepa Dinamani 
Reviewed-by: Arnd Bergmann 
Acked-by: Felipe Balbi 
Acked-by: Steven Whitehouse 
Acked-by: Ryusuke Konishi 
Acked-by: David Sterba 
Signed-off-by: Al Viro

tracefs: ->d_parent is never NULL or negative...

2016-05-29T20:22:07+00:00

Signed-off-by: Al Viro

wrappers for ->i_mutex access

2016-01-22T23:04:28+00:00

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro