user/sven/linux.git/kernel/sysctl.c, branch v5.4.300

sched/rt: Disallow writing invalid values to sched_rt_period_us

2024-03-01T12:13:33Z

commit 079be8fc630943d9fc70a97807feb73d169ee3fc upstream. The validation of the value written to sched_rt_period_us was broken because: - the sysclt_sched_rt_period is declared as unsigned int - parsed by proc_do_intvec() - the range is asserted after the value parsed by proc_do_intvec() Because of this negative values written to the file were written into a unsigned integer that were later on interpreted as large positive integers which did passed the check: if (sysclt_sched_rt_period <= 0) return EINVAL; This commit fixes the parsing by setting explicit range for both perid_us and runtime_us into the sched_rt_sysctls table and processes the values with proc_dointvec_minmax() instead. Alternatively if we wanted to use full range of unsigned int for the period value we would have to split the proc_handler and use proc_douintvec() for it however even the Documentation/scheduller/sched-rt-group.rst describes the range as 1 to INT_MAX. As far as I can tell the only problem this causes is that the sysctl file allows writing negative values which when read back may confuse userspace. There is also a LTP test being submitted for these sysctl files at: http://patchwork.ozlabs.org/project/ltp/patch/20230901144433.2526-1-chrubis@suse.cz/ Signed-off-by: Cyril Hrubis Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20231002115553.3007-2-chrubis@suse.cz [ pvorel: rebased for 5.4 ] Reviewed-by: Petr Vorel Signed-off-by: Petr Vorel Signed-off-by: Greg Kroah-Hartman

mm: allow a controlled amount of unfairness in the page lock

2023-08-30T14:27:26Z

commit 5ef64cc8987a9211d3f3667331ba3411a94ddc79 upstream. Commit 2a9127fcf229 ("mm: rewrite wait_on_page_bit_common() logic") made the page locking entirely fair, in that if a waiter came in while the lock was held, the lock would be transferred to the lockers strictly in order. That was intended to finally get rid of the long-reported watchdog failures that involved the page lock under extreme load, where a process could end up waiting essentially forever, as other page lockers stole the lock from under it. It also improved some benchmarks, but it ended up causing huge performance regressions on others, simply because fair lock behavior doesn't end up giving out the lock as aggressively, causing better worst-case latency, but potentially much worse average latencies and throughput. Instead of reverting that change entirely, this introduces a controlled amount of unfairness, with a sysctl knob to tune it if somebody needs to. But the default value should hopefully be good for any normal load, allowing a few rounds of lock stealing, but enforcing the strict ordering before the lock has been stolen too many times. There is also a hint from Matthieu Baerts that the fair page coloring may end up exposing an ABBA deadlock that is hidden by the usual optimistic lock stealing, and while the unfairness doesn't fix the fundamental issue (and I'm still looking at that), it avoids it in practice. The amount of unfairness can be modified by writing a new value to the 'sysctl_page_lock_unfairness' variable (default value of 5, exposed through /proc/sys/vm/page_lock_unfairness), but that is hopefully something we'd use mainly for debugging rather than being necessary for any deep system tuning. This whole issue has exposed just how critical the page lock can be, and how contended it gets under certain locks. And the main contention doesn't really seem to be anything related to IO (which was the origin of this lock), but for things like just verifying that the page file mapping is stable while faulting in the page into a page table. Link: https://lore.kernel.org/linux-fsdevel/ed8442fd-6f54-dd84-cd4a-941e8b7ee603@MichaelLarabel.com/ Link: https://www.phoronix.com/scan.php?page=article&item=linux-50-59&num=1 Link: https://lore.kernel.org/linux-fsdevel/c560a38d-8313-51fb-b1ec-e904bd8836bc@tessares.net/ Reported-and-tested-by: Michael Larabel Tested-by: Matthieu Baerts Cc: Dave Chinner Cc: Matthew Wilcox Cc: Chris Mason Cc: Jan Kara Cc: Amir Goldstein Signed-off-by: Linus Torvalds Signed-off-by: Saeed Mirzamohammadi Tested-by: Maximilian Heyne Signed-off-by: Greg Kroah-Hartman

proc: proc_skip_spaces() shouldn't think it is working on C strings

2022-12-08T10:23:06Z

commit bce9332220bd677d83b19d21502776ad555a0e73 upstream. proc_skip_spaces() seems to think it is working on C strings, and ends up being just a wrapper around skip_spaces() with a really odd calling convention. Instead of basing it on skip_spaces(), it should have looked more like proc_skip_char(), which really is the exact same function (except it skips a particular character, rather than whitespace). So use that as inspiration, odd coding and all. Now the calling convention actually makes sense and works for the intended purpose. Reported-and-tested-by: Kyle Zeng Acked-by: Eric Dumazet Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

proc: avoid integer type confusion in get_proc_long

2022-12-08T10:23:06Z

commit e6cfaf34be9fcd1a8285a294e18986bfc41a409c upstream. proc_get_long() is passed a size_t, but then assigns it to an 'int' variable for the length. Let's not do that, even if our IO paths are limited to MAX_RW_COUNT (exactly because of these kinds of type errors). So do the proper test in the rigth type. Reported-by: Kyle Zeng Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: sysctl: fix missing numa_stat when !CONFIG_HUGETLB_PAGE

2022-07-21T18:59:24Z

[ Upstream commit 43b5240ca6b33108998810593248186b1e3ae34a ] "numa_stat" should not be included in the scope of CONFIG_HUGETLB_PAGE, if CONFIG_HUGETLB_PAGE is not configured even if CONFIG_NUMA is configured, "numa_stat" is missed form /proc. Move it out of CONFIG_HUGETLB_PAGE to fix it. Fixes: 4518085e127d ("mm, sysctl: make NUMA stats configurable") Signed-off-by: Muchun Song Cc: Acked-by: Michal Hocko Acked-by: Mel Gorman Signed-off-by: Luis Chamberlain Signed-off-by: Sasha Levin

x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting

2022-03-11T10:22:37Z

commit 44a3918c8245ab10c6c9719dd12e7a8d291980d8 upstream. With unprivileged eBPF enabled, eIBRS (without retpoline) is vulnerable to Spectre v2 BHB-based attacks. When both are enabled, print a warning message and report it in the 'spectre_v2' sysfs vulnerabilities file. Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Reviewed-by: Thomas Gleixner [fllinden@amazon.com: backported to 5.4] Signed-off-by: Frank van der Linden Signed-off-by: Greg Kroah-Hartman

bpf: Add kconfig knob for disabling unpriv bpf by default

2022-02-16T11:52:49Z

commit 08389d888287c3823f80b0216766b71e17f0aba5 upstream. Add a kconfig knob which allows for unprivileged bpf to be disabled by default. If set, the knob sets /proc/sys/kernel/unprivileged_bpf_disabled to value of 2. This still allows a transition of 2 -> {0,1} through an admin. Similarly, this also still keeps 1 -> {1} behavior intact, so that once set to permanently disabled, it cannot be undone aside from a reboot. We've also added extra2 with max of 2 for the procfs handler, so that an admin still has a chance to toggle between 0 <-> 2. Either way, as an additional alternative, applications can make use of CAP_BPF that we added a while ago. Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/74ec548079189e4e4dffaeb42b8987bb3c852eee.1620765074.git.daniel@iogearbox.net [fllinden@amazon.com: backported to 5.4] Signed-off-by: Frank van der Linden Signed-off-by: Greg Kroah-Hartman

sysctl.c: fix underflow value setting risk in vm_table

2021-03-17T16:03:45Z

[ Upstream commit 3b3376f222e3ab58367d9dd405cafd09d5e37b7c ] Apart from subsystem specific .proc_handler handler, all ctl_tables with extra1 and extra2 members set should use proc_dointvec_minmax instead of proc_dointvec, or the limit set in extra* never work and potentially echo underflow values(negative numbers) is likely make system unstable. Especially vfs_cache_pressure and zone_reclaim_mode, -1 is apparently not a valid value, but we can set to them. And then kernel may crash. # echo -1 > /proc/sys/vm/vfs_cache_pressure Link: https://lkml.kernel.org/r/20201223105535.2875-1-linf@wangsu.com Signed-off-by: Lin Feng Cc: Alexey Dobriyan Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

kernel: sysctl: make drop_caches write-only

2020-01-04T18:18:32Z

[ Upstream commit 204cb79ad42f015312a5bbd7012d09c93d9b46fb ] Currently, the drop_caches proc file and sysctl read back the last value written, suggesting this is somehow a stateful setting instead of a one-time command. Make it write-only, like e.g. compact_memory. While mitigating a VM problem at scale in our fleet, there was confusion about whether writing to this file will permanently switch the kernel into a non-caching mode. This influences the decision making in a tense situation, where tens of people are trying to fix tens of thousands of affected machines: Do we need a rollback strategy? What are the performance implications of operating in a non-caching state for several days? It also caused confusion when the kernel team said we may need to write the file several times to make sure it's effective ("But it already reads back 3?"). Link: http://lkml.kernel.org/r/20191031221602.9375-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Chris Down Acked-by: Vlastimil Babka Acked-by: David Hildenbrand Acked-by: Michal Hocko Acked-by: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

parisc: sysctl.c: Use CONFIG_PARISC instead of __hppa_ define

2019-10-14T19:43:54Z

Signed-off-by: Helge Deller