kernel.git/arch/x86/include/asm/fpu, branch linux-4.16.y

signal: Unify and correct copy_siginfo_to_user32

2018-01-16T01:56:20Z

Among the existing architecture specific versions of copy_siginfo_to_user32 there are several different implementation problems. Some architectures fail to handle all of the cases in in the siginfo union. Some architectures perform a blind copy of the siginfo union when the si_code is negative. A blind copy suggests the data is expected to be in 32bit siginfo format, which means that receiving such a signal via signalfd won't work, or that the data is in 64bit siginfo and the code is copying nonsense to userspace. Create a single instance of copy_siginfo_to_user32 that all of the architectures can share, and teach it to handle all of the cases in the siginfo union correctly, with the assumption that siginfo is stored internally to the kernel is 64bit siginfo format. A special case is made for x86 x32 format. This is needed as presence of both x32 and ia32 on x86_64 results in two different 32bit signal formats. By allowing this small special case there winds up being exactly one code base that needs to be maintained between all of the architectures. Vastly increasing the testing base and the chances of finding bugs. As the x86 copy of copy_siginfo_to_user32 the call of the x86 signal_compat_build_tests were moved into sigaction_compat_abi, so that they will keep running. Signed-off-by: "Eric W. Biederman"

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55Z

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

x86/fpu: Introduce validate_xstate_header()

2017-09-26T07:43:45Z

Move validation of user-supplied xstate_header into a helper function, in preparation of calling it from both the ptrace and sigreturn syscall paths. The new function also considers it to be an error if *any* reserved bits are set, whereas before we were just clearing most of them silently. This should reduce the chance of bugs that fail to correctly validate user-supplied XSAVE areas. It also will expose any broken userspace programs that set the other reserved bits; this is desirable because such programs will lose compatibility with future CPUs and kernels if those bits are ever used for anything. (There shouldn't be any such programs, and in fact in the case where the compacted format is in use we were already validating xfeatures. But you never know...) Signed-off-by: Eric Biggers Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Dmitry Vyukov Cc: Eric Biggers Cc: Fenghua Yu Cc: Kees Cook Cc: Kevin Hao Cc: Linus Torvalds Cc: Michael Halcrow Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Wanpeng Li Cc: Yu-cheng Yu Cc: kernel-hardening@lists.openwall.com Link: http://lkml.kernel.org/r/20170924105913.9157-2-mingo@kernel.org Signed-off-by: Ingo Molnar

x86/fpu: Rename fpu__activate_fpstate_read/write() to fpu__prepare_[read|write]()

2017-09-26T07:43:44Z

As per the new nomenclature we don't 'activate' the FPU state anymore, we initialize it. So drop the _activate_fpstate name from these functions, which were a bit of a mouthful anyway, and name them: fpu__prepare_read() fpu__prepare_write() Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Eric Biggers Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar

x86/fpu: Rename fpu__activate_curr() to fpu__initialize()

2017-09-26T07:43:44Z

Rename this function to better express that it's all about initializing the FPU state of a task which goes hand in hand with the fpu::initialized field. Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Eric Biggers Cc: Fenghua Yu Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/20170923130016.21448-33-mingo@kernel.org Signed-off-by: Ingo Molnar

x86/fpu: Rename fpu::fpstate_active to fpu::initialized

2017-09-26T07:43:36Z

The x86 FPU code used to have a complex state machine where both the FPU registers and the FPU state context could be 'active' (or inactive) independently of each other - which enabled features like lazy FPU restore. Much of this complexity is gone in the current code: now we basically can have FPU-less tasks (kernel threads) that don't use (and save/restore) FPU state at all, plus full FPU users that save/restore directly with no laziness whatsoever. But the fpu::fpstate_active still carries bits of the old complexity - meanwhile this flag has become a simple flag that shows whether the FPU context saving area in the thread struct is initialized and used, or not. Rename it to fpu::initialized to express this simplicity in the name as well. Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Eric Biggers Cc: Fenghua Yu Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/20170923130016.21448-30-mingo@kernel.org Signed-off-by: Ingo Molnar

x86/fpu: Remove fpu__current_fpstate_write_begin/end()

2017-09-26T07:42:20Z

These functions are not used anymore, so remove them. Cc: Andrew Morton Cc: Andy Lutomirski Cc: Bobby Powers Cc: Borislav Petkov Cc: Dave Hansen Cc: Eric Biggers Cc: Fenghua Yu Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/20170923130016.21448-29-mingo@kernel.org Signed-off-by: Ingo Molnar

x86/fpu: Reinitialize FPU registers if restoring FPU state fails

2017-09-25T07:26:38Z

Userspace can change the FPU state of a task using the ptrace() or rt_sigreturn() system calls. Because reserved bits in the FPU state can cause the XRSTOR instruction to fail, the kernel has to carefully validate that no reserved bits or other invalid values are being set. Unfortunately, there have been bugs in this validation code. For example, we were not checking that the 'xcomp_bv' field in the xstate_header was 0. As-is, such bugs are exploitable to read the FPU registers of other processes on the system. To do so, an attacker can create a task, assign to it an invalid FPU state, then spin in a loop and monitor the values of the FPU registers. Because the task's FPU registers are not being restored, sometimes the FPU registers will have the values from another process. This is likely to continue to be a problem in the future because the validation done by the CPU instructions like XRSTOR is not immediately visible to kernel developers. Nor will invalid FPU states ever be encountered during ordinary use --- they will only be seen during fuzzing or exploits. There can even be reserved bits outside the xstate_header which are easy to forget about. For example, the MXCSR register contains reserved bits, which were not validated by the KVM_SET_XSAVE ioctl until commit a575813bfe4b ("KVM: x86: Fix load damaged SSEx MXCSR register"). Therefore, mitigate this class of vulnerability by restoring the FPU registers from init_fpstate if restoring from the task's state fails. We actually used to do this, but it was (perhaps unwisely) removed by commit 9ccc27a5d297 ("x86/fpu: Remove error return values from copy_kernel_to_*regs() functions"). This new patch is also a bit different. First, it only clears the registers, not also the bad in-memory state; this is simpler and makes it easier to make the mitigation cover all callers of __copy_kernel_to_fpregs(). Second, it does the register clearing in an exception handler so that no extra instructions are added to context switches. In fact, we *remove* instructions, since previously we were always zeroing the register containing 'err' even if CONFIG_X86_DEBUG_FPU was disabled. Signed-off-by: Eric Biggers Reviewed-by: Rik van Riel Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Dmitry Vyukov Cc: Eric Biggers Cc: Fenghua Yu Cc: Kevin Hao Cc: Linus Torvalds Cc: Michael Halcrow Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Wanpeng Li Cc: Yu-cheng Yu Cc: kernel-hardening@lists.openwall.com Link: http://lkml.kernel.org/r/20170922174156.16780-4-ebiggers3@gmail.com Link: http://lkml.kernel.org/r/20170923130016.21448-27-mingo@kernel.org Signed-off-by: Ingo Molnar

x86/fpu: Turn WARN_ON() in context switch into WARN_ON_FPU()

2017-09-24T11:04:35Z

copy_xregs_to_kernel checks if the alternatives have been already patched. This WARN_ON() is always executed in every context switch. All the other checks in fpu internal.h are WARN_ON_FPU(), but this one is plain WARN_ON(). I assume it was forgotten to switch it. So switch it to WARN_ON_FPU() too to avoid some unnecessary code in the context switch, and a potentially expensive cache line miss for the global variable. Signed-off-by: Andi Kleen Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Eric Biggers Cc: Fenghua Yu Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/20170329062605.4970-1-andi@firstfloor.org Link: http://lkml.kernel.org/r/20170923130016.21448-24-mingo@kernel.org Signed-off-by: Ingo Molnar

x86/fpu: Add FPU state copying quirk to handle XRSTOR failure on Intel Skylake CPUs

2017-09-24T11:04:34Z

On Skylake CPUs I noticed that XRSTOR is unable to deal with states created by copyout_from_xsaves() if the xstate has only SSE/YMM state, and no FP state. That is, xfeatures had XFEATURE_MASK_SSE set, but not XFEATURE_MASK_FP. The reason is that part of the SSE/YMM state lives in the MXCSR and MXCSR_FLAGS fields of the FP state. Ensure that whenever we copy SSE or YMM state around, the MXCSR and MXCSR_FLAGS fields are also copied around. Signed-off-by: Rik van Riel Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Dave Hansen Cc: Eric Biggers Cc: Fenghua Yu Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/20170210085445.0f1cc708@annuminas.surriel.com Link: http://lkml.kernel.org/r/20170923130016.21448-22-mingo@kernel.org Signed-off-by: Ingo Molnar