kernel/linux.git/fs/proc/proc_sysctl.c, branch v5.10.257

fix proc_sys_compare() handling of in-lookup dentries

2025-07-17T16:27:52+00:00

[ Upstream commit b969f9614885c20f903e1d1f9445611daf161d6d ] There's one case where ->d_compare() can be called for an in-lookup dentry; usually that's nothing special from ->d_compare() point of view, but... proc_sys_compare() is weird. The thing is, /proc/sys subdirectories can look differently for different processes. Up to and including having the same name resolve to different dentries - all of them hashed. The way it's done is ->d_compare() refusing to admit a match unless this dentry is supposed to be visible to this caller. The information needed to discriminate between them is stored in inode; it is set during proc_sys_lookup() and until it's done d_splice_alias() we really can't tell who should that dentry be visible for. Normally there's no negative dentries in /proc/sys; we can run into a dying dentry in RCU dcache lookup, but those can be safely rejected. However, ->d_compare() is also called for in-lookup dentries, before they get positive - or hashed, for that matter. In case of match we will wait until dentry leaves in-lookup state and repeat ->d_compare() afterwards. In other words, the right behaviour is to treat the name match as sufficient for in-lookup dentries; if dentry is not for us, we'll see that when we recheck once proc_sys_lookup() is done with it. While we are at it, fix the misspelled READ_ONCE and WRITE_ONCE there. Fixes: d9171b934526 ("parallel lookups machinery, part 4 (and last)") Reported-by: NeilBrown Reviewed-by: Christian Brauner Reviewed-by: NeilBrown Signed-off-by: Al Viro Signed-off-by: Sasha Levin

sysctl: always initialize i_uid/i_gid

2024-08-19T03:41:06+00:00

[ Upstream commit 98ca62ba9e2be5863c7d069f84f7166b45a5b2f4 ] Always initialize i_uid/i_gid inside the sysfs core so set_ownership() can safely skip setting them. Commit 5ec27ec735ba ("fs/proc/proc_sysctl.c: fix the default values of i_uid/i_gid on /proc/sys inodes.") added defaults for i_uid/i_gid when set_ownership() was not implemented. It also missed adjusting net_ctl_set_ownership() to use the same default values in case the computation of a better value failed. Fixes: 5ec27ec735ba ("fs/proc/proc_sysctl.c: fix the default values of i_uid/i_gid on /proc/sys inodes.") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh Signed-off-by: Joel Granados Signed-off-by: Sasha Levin

watchdog: move softlockup_panic back to early_param

2023-11-28T16:54:56+00:00

commit 8b793bcda61f6c3ed4f5b2ded7530ef6749580cb upstream. Setting softlockup_panic from do_sysctl_args() causes it to take effect later in boot. The lockup detector is enabled before SMP is brought online, but do_sysctl_args runs afterwards. If a user wants to set softlockup_panic on boot and have it trigger should a softlockup occur during onlining of the non-boot processors, they could do this prior to commit f117955a2255 ("kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases"). However, after this commit the value of softlockup_panic is set too late to be of help for this type of problem. Restore the prior behavior. Signed-off-by: Krister Johansen Cc: stable@vger.kernel.org Fixes: f117955a2255 ("kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases") Signed-off-by: Luis Chamberlain Signed-off-by: Greg Kroah-Hartman

sysctl: move some boundary constants from sysctl.c to sysctl_vals

2023-06-28T08:28:09+00:00

[ Upstream commit 78e36f3b0dae586f623c4a37ec5eb5496f5abbe1 ] sysctl has helpers which let us specify boundary values for a min or max int value. Since these are used for a boundary check only they don't change, so move these variables to sysctl_vals to avoid adding duplicate variables. This will help with our cleanup of kernel/sysctl.c. [akpm@linux-foundation.org: update it for "mm/pagealloc: sysctl: change watermark_scale_factor max limit to 30%"] [mcgrof@kernel.org: major rebase] Link: https://lkml.kernel.org/r/20211123202347.818157-3-mcgrof@kernel.org Signed-off-by: Xiaoming Ni Signed-off-by: Luis Chamberlain Reviewed-by: Kees Cook Cc: Al Viro Cc: Amir Goldstein Cc: Andy Shevchenko Cc: Benjamin LaHaise Cc: "Eric W. Biederman" Cc: Greg Kroah-Hartman Cc: Iurii Zaikin Cc: Jan Kara Cc: Paul Turner Cc: Peter Zijlstra Cc: Petr Mladek Cc: Qing Wang Cc: Sebastian Reichel Cc: Sergey Senozhatsky Cc: Stephen Kitt Cc: Tetsuo Handa Cc: Antti Palosaari Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Clemens Ladisch Cc: David Airlie Cc: Jani Nikula Cc: Joel Becker Cc: Joonas Lahtinen Cc: Joseph Qi Cc: Julia Lawall Cc: Lukas Middendorf Cc: Mark Fasheh Cc: Phillip Potter Cc: Rodrigo Vivi Cc: Douglas Gilbert Cc: James E.J. Bottomley Cc: Jani Nikula Cc: John Ogness Cc: Martin K. Petersen Cc: "Rafael J. Wysocki" Cc: Steven Rostedt (VMware) Cc: Suren Baghdasaryan Cc: "Theodore Ts'o" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Stable-dep-of: 935d44acf621 ("memfd: check for non-NULL file_seals in memfd_create() syscall") Signed-off-by: Sasha Levin

sysctl: add proc_dou8vec_minmax()

2023-04-20T10:10:26+00:00

[ Upstream commit cb9444130662c6c13022579c861098f212db2562 ] Networking has many sysctls that could fit in one u8. This patch adds proc_dou8vec_minmax() for this purpose. Note that the .extra1 and .extra2 fields are pointing to integers, because it makes conversions easier. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Stable-dep-of: dc5110c2d959 ("tcp: restrict net.ipv4.tcp_app_win") Signed-off-by: Sasha Levin

sysctl: add a new register_sysctl_init() interface

2023-02-01T07:23:18+00:00

commit 3ddd9a808cee7284931312f2f3e854c9617f44b2 upstream. Patch series "sysctl: first set of kernel/sysctl cleanups", v2. Finally had time to respin the series of the work we had started last year on cleaning up the kernel/sysct.c kitchen sink. People keeps stuffing their sysctls in that file and this creates a maintenance burden. So this effort is aimed at placing sysctls where they actually belong. I'm going to split patches up into series as there is quite a bit of work. This first set adds register_sysctl_init() for uses of registerting a sysctl on the init path, adds const where missing to a few places, generalizes common values so to be more easy to share, and starts the move of a few kernel/sysctl.c out where they belong. The majority of rework on v2 in this first patch set is 0-day fixes. Eric Biederman's feedback is later addressed in subsequent patch sets. I'll only post the first two patch sets for now. We can address the rest once the first two patch sets get completely reviewed / Acked. This patch (of 9): The kernel/sysctl.c is a kitchen sink where everyone leaves their dirty dishes, this makes it very difficult to maintain. To help with this maintenance let's start by moving sysctls to places where they actually belong. The proc sysctl maintainers do not want to know what sysctl knobs you wish to add for your own piece of code, we just care about the core logic. Today though folks heavily rely on tables on kernel/sysctl.c so they can easily just extend this table with their needed sysctls. In order to help users move their sysctls out we need to provide a helper which can be used during code initialization. We special-case the initialization use of register_sysctl() since it *is* safe to fail, given all that sysctls do is provide a dynamic interface to query or modify at runtime an existing variable. So the use case of register_sysctl() on init should *not* stop if the sysctls don't end up getting registered. It would be counter productive to stop boot if a simple sysctl registration failed. Provide a helper for init then, and document the recommended init levels to use for callers of this routine. We will later use this in subsequent patches to start slimming down kernel/sysctl.c tables and moving sysctl registration to the code which actually needs these sysctls. [mcgrof@kernel.org: major commit log and documentation rephrasing also moved to fs/proc/proc_sysctl.c ] Link: https://lkml.kernel.org/r/20211123202347.818157-1-mcgrof@kernel.org Link: https://lkml.kernel.org/r/20211123202347.818157-2-mcgrof@kernel.org Signed-off-by: Xiaoming Ni Signed-off-by: Luis Chamberlain Reviewed-by: Kees Cook Cc: Iurii Zaikin Cc: "Eric W. Biederman" Cc: Peter Zijlstra Cc: Greg Kroah-Hartman Cc: Paul Turner Cc: Andy Shevchenko Cc: Sebastian Reichel Cc: Tetsuo Handa Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Qing Wang Cc: Benjamin LaHaise Cc: Al Viro Cc: Jan Kara Cc: Amir Goldstein Cc: Stephen Kitt Cc: Antti Palosaari Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Clemens Ladisch Cc: David Airlie Cc: Jani Nikula Cc: Joel Becker Cc: Joonas Lahtinen Cc: Joseph Qi Cc: Julia Lawall Cc: Lukas Middendorf Cc: Mark Fasheh Cc: Phillip Potter Cc: Rodrigo Vivi Cc: Douglas Gilbert Cc: James E.J. Bottomley Cc: Jani Nikula Cc: John Ogness Cc: Martin K. Petersen Cc: "Rafael J. Wysocki" Cc: Steven Rostedt (VMware) Cc: Suren Baghdasaryan Cc: "Theodore Ts'o" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Eric Biggers Signed-off-by: Sasha Levin

proc: use kvzalloc for our kernel buffer

2021-03-04T10:38:21+00:00

[ Upstream commit 4508943794efdd94171549c0bd52810e2f4ad9fe ] Since sysctl: pass kernel pointers to ->proc_handler we have been pre-allocating a buffer to copy the data from the proc handlers into, and then copying that to userspace. The problem is this just blindly kzalloc()'s the buffer size passed in from the read, which in the case of our 'cat' binary was 64kib. Order-4 allocations are not awesome, and since we can potentially allocate up to our maximum order, so use kvzalloc for these buffers. [willy@infradead.org: changelog tweaks] Link: https://lkml.kernel.org/r/6345270a2c1160b89dd5e6715461f388176899d1.1612972413.git.josef@toxicpanda.com Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler") Signed-off-by: Josef Bacik Reviewed-by: Christoph Hellwig Acked-by: Vlastimil Babka Cc: Al Viro Cc: Alexey Dobriyan CC: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

proc_sysctl: fix oops caused by incorrect command parameters

2021-01-27T10:55:14+00:00

commit 697edcb0e4eadc41645fe88c991fe6a206b1a08d upstream. The process_sysctl_arg() does not check whether val is empty before invoking strlen(val). If the command line parameter () is incorrectly configured and val is empty, oops is triggered. For example: "hung_task_panic=1" is incorrectly written as "hung_task_panic", oops is triggered. The call stack is as follows: Kernel command line: .... hung_task_panic ...... Call trace: __pi_strlen+0x10/0x98 parse_args+0x278/0x344 do_sysctl_args+0x8c/0xfc kernel_init+0x5c/0xf4 ret_from_fork+0x10/0x30 To fix it, check whether "val" is empty when "phram" is a sysctl field. Error codes are returned in the failure branch, and error logs are generated by parse_args(). Link: https://lkml.kernel.org/r/20210118133029.28580-1-nixiaoming@huawei.com Fixes: 3db978d480e2843 ("kernel/sysctl: support setting sysctl parameters from kernel command line") Signed-off-by: Xiaoming Ni Acked-by: Vlastimil Babka Cc: Luis Chamberlain Cc: Kees Cook Cc: Iurii Zaikin Cc: Alexey Dobriyan Cc: Michal Hocko Cc: Masami Hiramatsu Cc: Heiner Kallweit Cc: Randy Dunlap Cc: [5.8+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

sysctl: Convert to iter interfaces

2020-09-09T02:20:39+00:00

Using the read_iter/write_iter interfaces allows for in-kernel users to set sysctls without using set_fs(). Also, the buffer is a string, so give it the real type of 'char *', not void *. [AV: Christoph's fixup folded in] Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Christoph Hellwig Signed-off-by: Al Viro

Call sysctl_head_finish on error

2020-07-03T18:10:46+00:00

This error path returned directly instead of calling sysctl_head_finish(). Fixes: ef9d965bc8b6 ("sysctl: reject gigantic reads/write to sysctl files") Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Al Viro