kernel.git/arch/x86/kernel/ldt.c, branch linux-4.12.y

Merge branch 'akpm' (patches from Andrew)

2016-12-13T04:50:02Z

Merge updates from Andrew Morton: - various misc bits - most of MM (quite a lot of MM material is awaiting the merge of linux-next dependencies) - kasan - printk updates - procfs updates - MAINTAINERS - /lib updates - checkpatch updates * emailed patches from Andrew Morton : (123 commits) init: reduce rootwait polling interval time to 5ms binfmt_elf: use vmalloc() for allocation of vma_filesz checkpatch: don't emit unified-diff error for rename-only patches checkpatch: don't check c99 types like uint8_t under tools checkpatch: avoid multiple line dereferences checkpatch: don't check .pl files, improve absolute path commit log test scripts/checkpatch.pl: fix spelling checkpatch: don't try to get maintained status when --no-tree is given lib/ida: document locking requirements a bit better lib/rbtree.c: fix typo in comment of ____rb_erase_color lib/Kconfig.debug: make CONFIG_STRICT_DEVMEM depend on CONFIG_DEVMEM MAINTAINERS: add drm and drm/i915 irc channels MAINTAINERS: add "C:" for URI for chat where developers hang out MAINTAINERS: add drm and drm/i915 bug filing info MAINTAINERS: add "B:" for URI where to file bugs get_maintainer: look for arbitrary letter prefixes in sections printk: add Kconfig option to set default console loglevel printk/sound: handle more message headers printk/btrfs: handle more message headers printk/kdb: handle more message headers ...

x86/ldt: use vfree_atomic() to free ldt entries

2016-12-13T02:55:08Z

vfree() is going to use sleeping lock. free_ldt_struct() may be called with disabled preemption, therefore we must use vfree_atomic() here. E.g. call trace: vfree() free_ldt_struct() destroy_context_ldt() __mmdrop() finish_task_switch() schedule_tail() ret_from_fork() Link: http://lkml.kernel.org/r/1479474236-4139-7-git-send-email-hch@lst.de Signed-off-by: Andrey Ryabinin Signed-off-by: Christoph Hellwig Cc: Joel Fernandes Cc: Jisheng Zhang Cc: Chris Wilson Cc: John Dias Cc: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

x86/ldt: Make all size computations unsigned

2016-12-09T23:24:39Z

ldt->size can never be negative. The helper functions take 'unsigned int' arguments which are assigned from ldt->size. The related user space user_desc struct member entry_number is unsigned as well. But ldt->size itself and a few local variables which are related to ldt->size are type 'int' which makes no sense whatsoever and results in typecasts which make the eyes bleed. Clean it up and convert everything which is related to ldt->size to unsigned it. Signed-off-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Dave Hansen Cc: Andrey Ryabinin Cc: Dan Carpenter

x86/ldt: Make a size argument unsigned

2016-12-09T23:24:39Z

My static checker complains that we put an upper bound on the "size" argument but not a lower bound. The checker is not smart enough to know the possible ranges of "old_mm->context.ldt->size" from init_new_context_ldt() so it thinks maybe it could be negative. Let's make it unsigned to silence the warning and future proof the code a bit. Signed-off-by: Dan Carpenter Acked-by: Andy Lutomirski Cc: Dave Hansen Cc: kernel-janitors@vger.kernel.org Cc: Andrey Ryabinin Cc: Andrew Morton Link: http://lkml.kernel.org/r/20161208105602.GA11382@elgon.mountain Signed-off-by: Thomas Gleixner

x86/mm: Factor out LDT init from context init

2016-02-18T18:46:31Z

The arch-specific mm_context_t is a great place to put protection-key allocation state. But, we need to initialize the allocation state because pkey 0 is always "allocated". All of the runtime initialization of mm_context_t is done in *_ldt() manipulation functions. This renames the existing LDT functions like this: init_new_context() -> init_new_context_ldt() destroy_context() -> destroy_context_ldt() and makes init_new_context() and destroy_context() available for generic use. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20160212210234.DB34FCC5@viggo.jf.intel.com Signed-off-by: Ingo Molnar

x86/ldt: Fix small LDT allocation for Xen

2015-09-14T10:10:50Z

While the following commit: 37868fe113 ("x86/ldt: Make modify_ldt synchronous") added a nice comment explaining that Xen needs page-aligned whole page chunks for guest descriptor tables, it then nevertheless used kzalloc() on the small size path. As I'm unaware of guarantees for kmalloc(PAGE_SIZE, ) to return page-aligned memory blocks, I believe this needs to be switched back to __get_free_page() (or better get_zeroed_page()). Signed-off-by: Jan Beulich Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: David Vrabel Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/55E735D6020000780009F1E6@prv-mh.provo.novell.com Signed-off-by: Ingo Molnar

x86/ldt: Make modify_ldt synchronous

2015-07-31T08:23:23Z

modify_ldt() has questionable locking and does not synchronize threads. Improve it: redesign the locking and synchronize all threads' LDTs using an IPI on all modifications. This will dramatically slow down modify_ldt in multithreaded programs, but there shouldn't be any multithreaded programs that care about modify_ldt's performance in the first place. This fixes some fallout from the CVE-2015-5157 fixes. Signed-off-by: Andy Lutomirski Reviewed-by: Borislav Petkov Cc: Andrew Cooper Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jan Beulich Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Sasha Levin Cc: Steven Rostedt Cc: Thomas Gleixner Cc: security@kernel.org Cc: Cc: xen-devel Link: http://lkml.kernel.org/r/4c6978476782160600471bd865b318db34c7b628.1438291540.git.luto@kernel.org Signed-off-by: Ingo Molnar

x86, espfix: Make it possible to disable 16-bit support

2014-05-04T19:27:37Z

Embedded systems, which may be very memory-size-sensitive, are extremely unlikely to ever encounter any 16-bit software, so make it a CONFIG_EXPERT option to turn off support for any 16-bit software whatsoever. Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com

x86-64, espfix: Don't leak bits 31:16 of %esp returning to 16-bit stack

2014-04-30T21:14:28Z

The IRET instruction, when returning to a 16-bit segment, only restores the bottom 16 bits of the user space stack pointer. This causes some 16-bit software to break, but it also leaks kernel state to user space. We have a software workaround for that ("espfix") for the 32-bit kernel, but it relies on a nonzero stack segment base which is not available in 64-bit mode. In checkin: b3b42ac2cbae x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels we "solved" this by forbidding 16-bit segments on 64-bit kernels, with the logic that 16-bit support is crippled on 64-bit kernels anyway (no V86 support), but it turns out that people are doing stuff like running old Win16 binaries under Wine and expect it to work. This works around this by creating percpu "ministacks", each of which is mapped 2^16 times 64K apart. When we detect that the return SS is on the LDT, we copy the IRET frame to the ministack and use the relevant alias to return to userspace. The ministacks are mapped readonly, so if IRET faults we promote #GP to #DF which is an IST vector and thus has its own stack; we then do the fixup in the #DF handler. (Making #GP an IST exception would make the msr_safe functions unsafe in NMI/MC context, and quite possibly have other effects.) Special thanks to: - Andy Lutomirski, for the suggestion of using very small stack slots and copy (as opposed to map) the IRET frame there, and for the suggestion to mark them readonly and let the fault promote to #DF. - Konrad Wilk for paravirt fixup and testing. - Borislav Petkov for testing help and useful comments. Reported-by: Brian Gerst Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com Cc: Konrad Rzeszutek Wilk Cc: Borislav Petkov Cc: Andrew Lutomriski Cc: Linus Torvalds Cc: Dirk Hohndel Cc: Arjan van de Ven Cc: comex Cc: Alexander van Heukelum Cc: Boris Ostrovsky Cc: # consider after upstream merge

x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels

2014-04-11T17:10:09Z

The IRET instruction, when returning to a 16-bit segment, only restores the bottom 16 bits of the user space stack pointer. We have a software workaround for that ("espfix") for the 32-bit kernel, but it relies on a nonzero stack segment base which is not available in 32-bit mode. Since 16-bit support is somewhat crippled anyway on a 64-bit kernel (no V86 mode), and most (if not quite all) 64-bit processors support virtualization for the users who really need it, simply reject attempts at creating a 16-bit segment when running on top of a 64-bit kernel. Cc: Linus Torvalds Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/n/tip-kicdm89kzw9lldryb1br9od0@git.kernel.org Cc: