kernel.git/arch/x86/entry, branch linux-4.19.y

x86/mm: Fix VDSO and VVAR placement on 5-level paging machines

2023-08-16T16:13:00Z

commit 1b8b1aa90c9c0e825b181b98b8d9e249dc395470 upstream. Yingcong has noticed that on the 5-level paging machine, VDSO and VVAR VMAs are placed above the 47-bit border: 8000001a9000-8000001ad000 r--p 00000000 00:00 0 [vvar] 8000001ad000-8000001af000 r-xp 00000000 00:00 0 [vdso] This might confuse users who are not aware of 5-level paging and expect all userspace addresses to be under the 47-bit border. So far problem has only been triggered with ASLR disabled, although it may also occur with ASLR enabled if the layout is randomized in a just right way. The problem happens due to custom placement for the VMAs in the VDSO code: vdso_addr() tries to place them above the stack and checks the result against TASK_SIZE_MAX, which is wrong. TASK_SIZE_MAX is set to the 56-bit border on 5-level paging machines. Use DEFAULT_MAP_WINDOW instead. Fixes: b569bab78d8d ("x86/mm: Prepare to expose larger address space to userspace") Reported-by: Yingcong Wu Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20230803151609.22141-1-kirill.shutemov%40linux.intel.com Signed-off-by: Greg Kroah-Hartman

exit: Add and use make_task_dead.

2023-02-06T06:49:45Z

commit 0e25498f8cd43c1b5aa327f373dd094e9a006da7 upstream. There are two big uses of do_exit. The first is it's design use to be the guts of the exit(2) system call. The second use is to terminate a task after something catastrophic has happened like a NULL pointer in kernel code. Add a function make_task_dead that is initialy exactly the same as do_exit to cover the cases where do_exit is called to handle catastrophic failure. In time this can probably be reduced to just a light wrapper around do_task_dead. For now keep it exactly the same so that there will be no behavioral differences introducing this new concept. Replace all of the uses of do_exit that use it for catastraphic task cleanup with make_task_dead to make it clear what the code is doing. As part of this rename rewind_stack_do_exit rewind_stack_and_make_dead. Signed-off-by: "Eric W. Biederman" Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman

x86/entry/64: Add instruction suffix to SYSRET

2023-02-06T06:49:44Z

commit b2b1d94cdfd4e906d3936dab2850096a4a0c2017 upstream. ignore_sysret() contains an unsuffixed SYSRET instruction. gas correctly interprets this as SYSRETL, but leaving it up to gas to guess when there is no register operand that implies a size is bad practice, and upstream gas is likely to warn about this in the future. Use SYSRETL explicitly. This does not change the assembled output. Signed-off-by: Jan Beulich Signed-off-by: Borislav Petkov Acked-by: Andy Lutomirski Link: https://lkml.kernel.org/r/038a7c35-062b-a285-c6d2-653b56585844@suse.com Signed-off-by: Greg Kroah-Hartman

x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

2022-11-23T06:53:45Z

commit b2620facef4889fefcbf2e87284f34dcd4189bce upstream. If a kernel is built with CONFIG_RETPOLINE=n, but the user still wants to mitigate Spectre v2 using IBRS or eIBRS, the RSB filling will be silently disabled. There's nothing retpoline-specific about RSB buffer filling. Remove the CONFIG_RETPOLINE guards around it. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Suleiman Souhlal Signed-off-by: Greg Kroah-Hartman

x86/entry: Add kernel IBRS implementation

2022-11-23T06:53:45Z

commit 2dbb887e875b1de3ca8f40ddf26bcfe55798c609 upstream. Implement Kernel IBRS - currently the only known option to mitigate RSB underflow speculation issues on Skylake hardware. Note: since IBRS_ENTER requires fuller context established than UNTRAIN_RET, it must be placed after it. However, since UNTRAIN_RET itself implies a RET, it must come after IBRS_ENTER. This means IBRS_ENTER needs to also move UNTRAIN_RET. Note 2: KERNEL_IBRS is sub-optimal for XenPV. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov [cascardo: conflict at arch/x86/entry/entry_64.S, skip_r11rcx] [cascardo: conflict at arch/x86/entry/entry_64_compat.S] [cascardo: conflict fixups, no ANNOTATE_NOENDBR] [cascardo: entry fixups because of missing UNTRAIN_RET] [cascardo: conflicts on fsgsbase] Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Suleiman Souhlal Signed-off-by: Greg Kroah-Hartman

x86/entry: Remove skip_r11rcx

2022-11-23T06:53:44Z

commit 1b331eeea7b8676fc5dbdf80d0a07e41be226177 upstream. Yes, r11 and rcx have been restored previously, but since they're being popped anyway (into rsi) might as well pop them into their own regs -- setting them to the value they already are. Less magical code. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220506121631.365070674@infradead.org Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Suleiman Souhlal Signed-off-by: Greg Kroah-Hartman

x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments

2022-08-25T09:14:50Z

commit ffcf9c5700e49c0aee42dcba9a12ba21338e8136 upstream. Users of GNU ld (BFD) from binutils 2.39+ will observe multiple instances of a new warning when linking kernels in the form: ld: warning: arch/x86/boot/pmjump.o: missing .note.GNU-stack section implies executable stack ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker ld: warning: arch/x86/boot/compressed/vmlinux has a LOAD segment with RWX permissions Generally, we would like to avoid the stack being executable. Because there could be a need for the stack to be executable, assembler sources have to opt-in to this security feature via explicit creation of the .note.GNU-stack feature (which compilers create by default) or command line flag --noexecstack. Or we can simply tell the linker the production of such sections is irrelevant and to link the stack as --noexecstack. LLVM's LLD linker defaults to -z noexecstack, so this flag isn't strictly necessary when linking with LLD, only BFD, but it doesn't hurt to be explicit here for all linkers IMO. --no-warn-rwx-segments is currently BFD specific and only available in the current latest release, so it's wrapped in an ld-option check. While the kernel makes extensive usage of ELF sections, it doesn't use permissions from ELF segments. Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/ Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107 Link: https://github.com/llvm/llvm-project/issues/57009 Reported-and-tested-by: Jens Axboe Suggested-by: Fangrui Song Signed-off-by: Nick Desaulniers Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

x86: Fix return value of __setup handlers

2022-06-14T14:59:21Z

[ Upstream commit 12441ccdf5e2f5a01a46e344976cbbd3d46845c9 ] __setup() handlers should return 1 to obsolete_checksetup() in init/main.c to indicate that the boot option has been handled. A return of 0 causes the boot option/value to be listed as an Unknown kernel parameter and added to init's (limited) argument (no '=') or environment (with '=') strings. So return 1 from these x86 __setup handlers. Examples: Unknown kernel command line parameters "apicpmtimer BOOT_IMAGE=/boot/bzImage-517rc8 vdso=1 ring3mwait=disable", will be passed to user space. Run /sbin/init as init process with arguments: /sbin/init apicpmtimer with environment: HOME=/ TERM=linux BOOT_IMAGE=/boot/bzImage-517rc8 vdso=1 ring3mwait=disable Fixes: 2aae950b21e4 ("x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu") Fixes: 77b52b4c5c66 ("x86: add "debugpat" boot option") Fixes: e16fd002afe2 ("x86/cpufeature: Enable RING3MWAIT for Knights Landing") Fixes: b8ce33590687 ("x86_64: convert to clock events") Reported-by: Igor Zhbanov Signed-off-by: Randy Dunlap Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru Link: https://lore.kernel.org/r/20220314012725.26661-1-rdunlap@infradead.org Signed-off-by: Sasha Levin

x86/cpu: Initialize MSR_TSC_AUX if RDTSCP or RDPID is supported

2021-05-22T08:59:26Z

commit b6b4fbd90b155a0025223df2c137af8a701d53b3 upstream. Initialize MSR_TSC_AUX with CPU node information if RDTSCP or RDPID is supported. This fixes a bug where vdso_read_cpunode() will read garbage via RDPID if RDPID is supported but RDTSCP is not. While no known CPU supports RDPID but not RDTSCP, both Intel's SDM and AMD's APM allow for RDPID to exist without RDTSCP, e.g. it's technically a legal CPU model for a virtual machine. Note, technically MSR_TSC_AUX could be initialized if and only if RDPID is supported since RDTSCP is currently not used to retrieve the CPU node. But, the cost of the superfluous WRMSR is negigible, whereas leaving MSR_TSC_AUX uninitialized is just asking for future breakage if someone decides to utilize RDTSCP. Fixes: a582c540ac1b ("x86/vdso: Use RDPID in preference to LSL when available") Signed-off-by: Sean Christopherson Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210504225632.1532621-2-seanjc@google.com Signed-off-by: Greg Kroah-Hartman

x86/unwind/orc: Fix premature unwind stoppage due to IRET frames

2020-05-14T05:57:23Z

commit 81b67439d147677d844d492fcbd03712ea438f42 upstream. The following execution path is possible: fsnotify() [ realign the stack and store previous SP in R10 ] [ only IRET regs saved ] common_interrupt() interrupt_entry() [ full pt_regs saved ] ... [ unwind stack ] When the unwinder goes through the NMI and the IRQ on the stack, and then sees fsnotify(), it doesn't have access to the value of R10, because it only has the five IRET registers. So the unwind stops prematurely. However, because the interrupt_entry() code is careful not to clobber R10 before saving the full regs, the unwinder should be able to read R10 from the previously saved full pt_regs associated with the NMI. Handle this case properly. When encountering an IRET regs frame immediately after a full pt_regs frame, use the pt_regs as a backup which can be used to get the C register values. Also, note that a call frame resets the 'prev_regs' value, because a function is free to clobber the registers. For this fix to work, the IRET and full regs frames must be adjacent, with no FUNC frames in between. So replace the FUNC hint in interrupt_entry() with an IRET_REGS hint. Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder") Reviewed-by: Miroslav Benes Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Dave Jones Cc: Jann Horn Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vince Weaver Link: https://lore.kernel.org/r/97a408167cc09f1cfa0de31a7b70dd88868d743f.1587808742.git.jpoimboe@redhat.com Signed-off-by: Greg Kroah-Hartman