user/sven/linux.git/include/linux/fs_context.h, branch v5.10.204

devtmpfs regression fix: reconfigure on each mount

2022-01-20T08:17:49Z

commit a6097180d884ddab769fb25588ea8598589c218c upstream. Prior to Linux v5.4 devtmpfs used mount_single() which treats the given mount options as "remount" options, so it updates the configuration of the single super_block on each mount. Since that was changed, the mount options used for devtmpfs are ignored. This is a regression which affect systemd - which mounts devtmpfs with "-o mode=755,size=4m,nr_inodes=1m". This patch restores the "remount" effect by calling reconfigure_single() Fixes: d401727ea0d7 ("devtmpfs: don't mix {ramfs,shmem}_fill_super() with mount_single()") Acked-by: Christian Brauner Cc: Al Viro Signed-off-by: NeilBrown Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

cgroup1: fix leaked context root causing sporadic NULL deref in LTP

2021-07-31T06:16:11Z

commit 1e7107c5ef44431bc1ebbd4c353f1d7c22e5f2ec upstream. Richard reported sporadic (roughly one in 10 or so) null dereferences and other strange behaviour for a set of automated LTP tests. Things like: BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 1516 Comm: umount Not tainted 5.10.0-yocto-standard #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014 RIP: 0010:kernfs_sop_show_path+0x1b/0x60 ...or these others: RIP: 0010:do_mkdirat+0x6a/0xf0 RIP: 0010:d_alloc_parallel+0x98/0x510 RIP: 0010:do_readlinkat+0x86/0x120 There were other less common instances of some kind of a general scribble but the common theme was mount and cgroup and a dubious dentry triggering the NULL dereference. I was only able to reproduce it under qemu by replicating Richard's setup as closely as possible - I never did get it to happen on bare metal, even while keeping everything else the same. In commit 71d883c37e8d ("cgroup_do_mount(): massage calling conventions") we see this as a part of the overall change: -------------- struct cgroup_subsys *ss; - struct dentry *dentry; [...] - dentry = cgroup_do_mount(&cgroup_fs_type, fc->sb_flags, root, - CGROUP_SUPER_MAGIC, ns); [...] - if (percpu_ref_is_dying(&root->cgrp.self.refcnt)) { - struct super_block *sb = dentry->d_sb; - dput(dentry); + ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns); + if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) { + struct super_block *sb = fc->root->d_sb; + dput(fc->root); deactivate_locked_super(sb); msleep(10); return restart_syscall(); } -------------- In changing from the local "*dentry" variable to using fc->root, we now export/leave that dentry pointer in the file context after doing the dput() in the unlikely "is_dying" case. With LTP doing a crazy amount of back to back mount/unmount [testcases/bin/cgroup_regression_5_1.sh] the unlikely becomes slightly likely and then bad things happen. A fix would be to not leave the stale reference in fc->root as follows: -------------- dput(fc->root); + fc->root = NULL; deactivate_locked_super(sb); -------------- ...but then we are just open-coding a duplicate of fc_drop_locked() so we simply use that instead. Cc: Al Viro Cc: Tejun Heo Cc: Zefan Li Cc: Johannes Weiner Cc: stable@vger.kernel.org # v5.1+ Reported-by: Richard Purdie Fixes: 71d883c37e8d ("cgroup_do_mount(): massage calling conventions") Signed-off-by: Paul Gortmaker Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

fuse: reject options on reconfigure via fsconfig(2)

2020-07-14T12:45:41Z

Previous patch changed handling of remount/reconfigure to ignore all options, including those that are unknown to the fuse kernel fs. This was done for backward compatibility, but this likely only affects the old mount(2) API. The new fsconfig(2) based reconfiguration could possibly be improved. This would make the new API less of a drop in replacement for the old, OTOH this is a good chance to get rid of some weirdnesses in the old API. Several other behaviors might make sense: 1) unknown options are rejected, known options are ignored 2) unknown options are rejected, known options are rejected if the value is changed, allowed otherwise 3) all options are rejected Prior to the backward compatibility fix to ignore all options all known options were accepted (1), even if they change the value of a mount parameter; fuse_reconfigure() does not look at the config values set by fuse_parse_param(). To fix that we'd need to verify that the value provided is the same as set in the initial configuration (2). The major drawback is that this is much more complex than just rejecting all attempts at changing options (3); i.e. all options signify initial configuration values and don't make sense on reconfigure. This patch opts for (3) with the rationale that no mount options are reconfigurable in fuse. Signed-off-by: Miklos Szeredi

docs: filesystems: convert mount_api.txt to ReST

2020-05-05T15:22:23Z

- Add a SPDX header; - Adjust document and section titles; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add table markups; - Add lists markups; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab Link: https://lore.kernel.org/r/32332c1659a28c22561cb5e64162c959856066b4.1588021877.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet

prefix-handling analogues of errorf() and friends

2020-02-07T19:48:39Z

called errorfc/infofc/warnfc/invalfc Signed-off-by: Al Viro

add prefix to fs_context->log

2020-02-07T19:48:35Z

... turning it into struct p_log embedded into fs_context. Initialize the prefix with fs_type->name, turning fs_parse() into a trivial inline wrapper for __fs_parse(). This makes fs_parameter_description->name completely unused. Signed-off-by: Al Viro

new primitive: __fs_parse()

2020-02-07T19:48:34Z

fs_parse() analogue taking p_log instead of fs_context. fs_parse() turned into a wrapper, callers in ceph_common and rbd switched to __fs_parse(). As the result, fs_parse() never gets NULL fs_context and neither do fs_context-based logging primitives Signed-off-by: Al Viro

struct p_log, variants of warnf() et.al. taking that one instead

2020-02-07T19:48:32Z

primitives for prefixed logging Signed-off-by: Al Viro

teach logfc() to handle prefices, give it saner calling conventions

2020-02-07T19:48:32Z

Signed-off-by: Al Viro

get rid of fs_value_is_filename_empty

2020-02-07T19:48:30Z

Its behaviour is identical to that of fs_value_is_filename. It makes no sense, anyway - LOOKUP_EMPTY affects nothing whatsoever once the pathname has been imported from userland. And both fs_value_is_filename and fs_value_is_filename_empty carry an already imported pathname. Signed-off-by: Al Viro