kernel/git/stable/linux.git/Documentation/admin-guide/kernel-parameters.txt, branch linux-5.9.y

USB: UAS: introduce a quirk to set no_write_same

2020-12-21T12:28:20+00:00

commit 8010622c86ca5bb44bc98492f5968726fc7c7a21 upstream. UAS does not share the pessimistic assumption storage is making that devices cannot deal with WRITE_SAME. A few devices supported by UAS, are reported to not deal well with WRITE_SAME. Those need a quirk. Add it to the device that needs it. Reported-by: David C. Partridge Signed-off-by: Oliver Neukum Cc: stable Link: https://lore.kernel.org/r/20201209152639.9195-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman

powerpc/64s: flush L1D after user accesses

2020-11-22T09:15:32+00:00

commit 9a32a7e78bd0cd9a9b6332cbdc345ee5ffd0c5de upstream. IBM Power9 processors can speculatively operate on data in the L1 cache before it has been completely validated, via a way-prediction mechanism. It is not possible for an attacker to determine the contents of impermissible memory using this method, since these systems implement a combination of hardware and software security measures to prevent scenarios where protected data could be leaked. However these measures don't address the scenario where an attacker induces the operating system to speculatively execute instructions using data that the attacker controls. This can be used for example to speculatively bypass "kernel user access prevention" techniques, as discovered by Anthony Steinhauser of Google's Safeside Project. This is not an attack by itself, but there is a possibility it could be used in conjunction with side-channels or other weaknesses in the privileged code to construct an attack. This issue can be mitigated by flushing the L1 cache between privilege boundaries of concern. This patch flushes the L1 cache after user accesses. This is part of the fix for CVE-2020-4788. Signed-off-by: Nicholas Piggin Signed-off-by: Daniel Axtens Signed-off-by: Greg Kroah-Hartman

powerpc/64s: flush L1D on kernel entry

2020-11-22T09:15:32+00:00

commit f79643787e0a0762d2409b7b8334e83f22d85695 upstream. IBM Power9 processors can speculatively operate on data in the L1 cache before it has been completely validated, via a way-prediction mechanism. It is not possible for an attacker to determine the contents of impermissible memory using this method, since these systems implement a combination of hardware and software security measures to prevent scenarios where protected data could be leaked. However these measures don't address the scenario where an attacker induces the operating system to speculatively execute instructions using data that the attacker controls. This can be used for example to speculatively bypass "kernel user access prevention" techniques, as discovered by Anthony Steinhauser of Google's Safeside Project. This is not an attack by itself, but there is a possibility it could be used in conjunction with side-channels or other weaknesses in the privileged code to construct an attack. This issue can be mitigated by flushing the L1 cache between privilege boundaries of concern. This patch flushes the L1 cache on kernel entry. This is part of the fix for CVE-2020-4788. Signed-off-by: Nicholas Piggin Signed-off-by: Daniel Axtens Signed-off-by: Greg Kroah-Hartman

xen/events: defer eoi in case of excessive number of events

2020-11-05T10:51:08+00:00

commit e99502f76271d6bc4e374fe368c50c67a1fd3070 upstream. In case rogue guests are sending events at high frequency it might happen that xen_evtchn_do_upcall() won't stop processing events in dom0. As this is done in irq handling a crash might be the result. In order to avoid that, delay further inter-domain events after some time in xen_evtchn_do_upcall() by forcing eoi processing into a worker on the same cpu, thus inhibiting new events coming in. The time after which eoi processing is to be delayed is configurable via a new module parameter "event_loop_timeout" which specifies the maximum event loop time in jiffies (default: 2, the value was chosen after some tests showing that a value of 2 was the lowest with an only slight drop of dom0 network throughput while multiple guests performed an event storm). How long eoi processing will be delayed can be specified via another parameter "event_eoi_delay" (again in jiffies, default 10, again the value was chosen after testing with different delay values). This is part of XSA-332. Cc: stable@vger.kernel.org Reported-by: Julien Grall Signed-off-by: Juergen Gross Reviewed-by: Stefano Stabellini Reviewed-by: Wei Liu Signed-off-by: Greg Kroah-Hartman

x86/fpu: Allow multiple bits in clearcpuid= parameter

2020-10-29T09:11:00+00:00

[ Upstream commit 0a4bb5e5507a585532cc413125b921c8546fc39f ] Commit 0c2a3913d6f5 ("x86/fpu: Parse clearcpuid= as early XSAVE argument") changed clearcpuid parsing from __setup() to cmdline_find_option(). While the __setup() function would have been called for each clearcpuid= parameter on the command line, cmdline_find_option() will only return the last one, so the change effectively made it impossible to disable more than one bit. Allow a comma-separated list of bit numbers as the argument for clearcpuid to allow multiple bits to be disabled again. Log the bits being disabled for informational purposes. Also fix the check on the return value of cmdline_find_option(). It returns -1 when the option is not found, so testing as a boolean is incorrect. Fixes: 0c2a3913d6f5 ("x86/fpu: Parse clearcpuid= as early XSAVE argument") Signed-off-by: Arvind Sankar Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20200907213919.2423441-1-nivedita@alum.mit.edu Signed-off-by: Sasha Levin

Documentation: efi: remove description of efi=old_map

2020-08-20T09:18:36+00:00

The old EFI runtime region mapping logic that was kept around for some time has finally been removed entirely, along with the SGI UV1 support code that was its last remaining user. So remove any mention of the efi=old_map command line parameter from the docs. Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Signed-off-by: Ard Biesheuvel

Merge tag 'docs-5.9-2' of git://git.lwn.net/linux

2020-08-13T20:57:45+00:00

Pull documentation fixes from Jonathan Corbet: "A handful of obvious fixes that wandered in during the merge window" * tag 'docs-5.9-2' of git://git.lwn.net/linux: Documentation/locking/locktypes: fix the typo doc/zh_CN: resolve undefined label warning in admin-guide index doc/zh_CN: fix title heading markup in admin-guide cpu-load docs: remove the 2.6 "Upgrading I2C Drivers" guide docs: Correct the release date of 5.2 stable mailmap: Update comments for with format and more detalis docs: cdrom: Fix a typo and rst markup Doc: admin-guide: use correct legends in kernel-parameters.txt Documentation/features: refresh RISC-V arch support files documentation: coccinelle: Improve command example for make C={1,2} Core-api: Documentation: Replace deprecated :c:func: Usage Dev-tools: Documentation: Replace deprecated :c:func: Usage Filesystems: Documentation: Replace deprecated :c:func: Usage docs: trace: fix a typo

Doc: admin-guide: use correct legends in kernel-parameters.txt

2020-08-11T16:41:35+00:00

Documentation/admin-guide/kernel-parameters.rst includes a legend telling us what configurations or hardware platforms are relevant for certain boot options. For X86, it is spelled "X86" and for x86_64, it is spelled "X86-64", so make corrections for those. Signed-off-by: Randy Dunlap Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: x86@kernel.org Link: https://lore.kernel.org/r/20200810024941.30231-1-rdunlap@infradead.org Signed-off-by: Jonathan Corbet

Merge branch 'akpm' (patches from Andrew)

2020-08-07T18:39:33+00:00

Merge misc updates from Andrew Morton: - a few MM hotfixes - kthread, tools, scripts, ntfs and ocfs2 - some of MM Subsystems affected by this patch series: kthread, tools, scripts, ntfs, ocfs2 and mm (hofixes, pagealloc, slab-generic, slab, slub, kcsan, debug, pagecache, gup, swap, shmem, memcg, pagemap, mremap, mincore, sparsemem, vmalloc, kasan, pagealloc, hugetlb and vmscan). * emailed patches from Andrew Morton : (162 commits) mm: vmscan: consistent update to pgrefill mm/vmscan.c: fix typo khugepaged: khugepaged_test_exit() check mmget_still_valid() khugepaged: retract_page_tables() remember to test exit khugepaged: collapse_pte_mapped_thp() protect the pmd lock khugepaged: collapse_pte_mapped_thp() flush the right range mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible mm: thp: replace HTTP links with HTTPS ones mm/page_alloc: fix memalloc_nocma_{save/restore} APIs mm/page_alloc.c: skip setting nodemask when we are in interrupt mm/page_alloc: fallbacks at most has 3 elements mm/page_alloc: silence a KASAN false positive mm/page_alloc.c: remove unnecessary end_bitidx for [set|get]_pfnblock_flags_mask() mm/page_alloc.c: simplify pageblock bitmap access mm/page_alloc.c: extract the common part in pfn_to_bitidx() mm/page_alloc.c: replace the definition of NR_MIGRATETYPE_BITS with PB_migratetype_bits mm/shuffle: remove dynamic reconfiguration mm/memory_hotplug: document why shuffle_zone() is relevant mm/page_alloc: remove nr_free_pagecache_pages() mm: remove vm_total_pages ...

mm, slub: extend slub_debug syntax for multiple blocks

2020-08-07T18:33:22+00:00

Patch series "slub_debug fixes and improvements". The slub_debug kernel boot parameter can either apply a single set of options to all caches or a list of caches. There is a use case where debugging is applied for all caches and then disabled at runtime for specific caches, for performance and memory consumption reasons [1]. As runtime changes are dangerous, extend the boot parameter syntax so that multiple blocks of either global or slab-specific options can be specified, with blocks delimited by ';'. This will also support the use case of [1] without runtime changes. For details see the updated Documentation/vm/slub.rst [1] https://lore.kernel.org/r/1383cd32-1ddc-4dac-b5f8-9c42282fa81c@codeaurora.org [weiyongjun1@huawei.com: make parse_slub_debug_flags() static] Link: http://lkml.kernel.org/r/20200702150522.4940-1-weiyongjun1@huawei.com Signed-off-by: Vlastimil Babka Signed-off-by: Andrew Morton Reviewed-by: Kees Cook Cc: Vlastimil Babka Cc: Christoph Lameter Cc: Jann Horn Cc: Roman Gushchin Cc: Vijayanand Jitta Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Link: http://lkml.kernel.org/r/20200610163135.17364-2-vbabka@suse.cz Signed-off-by: Linus Torvalds