kernel/linux.git/arch/x86/lib, branch v5.15.209

x86: remove __range_not_ok()

2026-01-19T12:10:12+00:00

commit 36903abedfe8d419e90ce349b2b4ce6dc2883e17 upstream. The __range_not_ok() helper is an x86 (and sparc64) specific interface that does roughly the same thing as __access_ok(), but with different calling conventions. Change this to use the normal interface in order for consistency as we clean up all access_ok() implementations. This changes the limit from TASK_SIZE to TASK_SIZE_MAX, which Al points out is the right thing do do here anyway. The callers have to use __access_ok() instead of the normal access_ok() though, because on x86 that contains a WARN_ON_IN_IRQ() check that cannot be used inside of NMI context while tracing. The check in copy_code() is not needed any more, because this one is already done by copy_from_user_nmi(). Suggested-by: Al Viro Suggested-by: Christoph Hellwig Link: https://lore.kernel.org/lkml/YgsUKcXGR7r4nINj@zeniv-ca.linux.org.uk/ Signed-off-by: Arnd Bergmann Stable-dep-of: d319f344561d ("mm: Fix copy_from_user_nofault().") Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman

x86/its: Add support for ITS-safe return thunk

2025-05-22T12:08:23+00:00

commit a75bf27fe41abe658c53276a0c486c4bf9adecfc upstream. RETs in the lower half of cacheline may be affected by ITS bug, specifically when the RSB-underflows. Use ITS-safe return thunk for such RETs. RETs that are not patched: - RET in retpoline sequence does not need to be patched, because the sequence itself fills an RSB before RET. - RETs in .init section are not reachable after init. - RETs that are explicitly marked safe with ANNOTATE_UNRET_SAFE. Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Josh Poimboeuf Reviewed-by: Alexandre Chartre Signed-off-by: Greg Kroah-Hartman

x86/its: Add support for ITS-safe indirect thunk

2025-05-22T12:08:23+00:00

commit 8754e67ad4ac692c67ff1f99c0d07156f04ae40c upstream. Due to ITS, indirect branches in the lower half of a cacheline may be vulnerable to branch target injection attack. Introduce ITS-safe thunks to patch indirect branches in the lower half of cacheline with the thunk. Also thunk any eBPF generated indirect branches in emit_indirect_jump(). Below category of indirect branches are not mitigated: - Indirect branches in the .init section are not mitigated because they are discarded after boot. - Indirect branches that are explicitly marked retpoline-safe. Note that retpoline also mitigates the indirect branches against ITS. This is because the retpoline sequence fills an RSB entry before RET, and it does not suffer from RSB-underflow part of the ITS. Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Josh Poimboeuf Reviewed-by: Alexandre Chartre Signed-off-by: Greg Kroah-Hartman

x86/insn: Fix PUSH instruction in x86 instruction decoder opcode map

2024-06-16T11:39:31+00:00

[ Upstream commit 59162e0c11d7257cde15f907d19fefe26da66692 ] The x86 instruction decoder is used not only for decoding kernel instructions. It is also used by perf uprobes (user space probes) and by perf tools Intel Processor Trace decoding. Consequently, it needs to support instructions executed by user space also. Opcode 0x68 PUSH instruction is currently defined as 64-bit operand size only i.e. (d64). That was based on Intel SDM Opcode Map. However that is contradicted by the Instruction Set Reference section for PUSH in the same manual. Remove 64-bit operand size only annotation from opcode 0x68 PUSH instruction. Example: $ cat pushw.s .global _start .text _start: pushw $0x1234 mov $0x1,%eax # system call number (sys_exit) int $0x80 $ as -o pushw.o pushw.s $ ld -s -o pushw pushw.o $ objdump -d pushw | tail -4 0000000000401000 <.text>: 401000: 66 68 34 12 pushw $0x1234 401004: b8 01 00 00 00 mov $0x1,%eax 401009: cd 80 int $0x80 $ perf record -e intel_pt//u ./pushw [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.014 MB perf.data ] Before: $ perf script --insn-trace=disasm Warning: 1 instruction trace errors pushw 10349 [000] 10586.869237014: 401000 [unknown] (/home/ahunter/git/misc/rtit-tests/pushw) pushw $0x1234 pushw 10349 [000] 10586.869237014: 401006 [unknown] (/home/ahunter/git/misc/rtit-tests/pushw) addb %al, (%rax) pushw 10349 [000] 10586.869237014: 401008 [unknown] (/home/ahunter/git/misc/rtit-tests/pushw) addb %cl, %ch pushw 10349 [000] 10586.869237014: 40100a [unknown] (/home/ahunter/git/misc/rtit-tests/pushw) addb $0x2e, (%rax) instruction trace error type 1 time 10586.869237224 cpu 0 pid 10349 tid 10349 ip 0x40100d code 6: Trace doesn't match instruction After: $ perf script --insn-trace=disasm pushw 10349 [000] 10586.869237014: 401000 [unknown] (./pushw) pushw $0x1234 pushw 10349 [000] 10586.869237014: 401004 [unknown] (./pushw) movl $1, %eax Fixes: eb13296cfaf6 ("x86: Instruction decoder API") Signed-off-by: Adrian Hunter Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20240502105853.5338-3-adrian.hunter@intel.com Signed-off-by: Sasha Levin

x86/retpoline: Do the necessary fixup to the Zen3/4 srso return thunk for !SRSO

2024-04-10T14:19:43+00:00

Commit 0e110732473e14d6520e49d75d2c88ef7d46fe67 upstream. The srso_alias_untrain_ret() dummy thunk in the !CONFIG_MITIGATION_SRSO case is there only for the altenative in CALL_UNTRAIN_RET to have a symbol to resolve. However, testing with kernels which don't have CONFIG_MITIGATION_SRSO enabled, leads to the warning in patch_return() to fire: missing return thunk: srso_alias_untrain_ret+0x0/0x10-0x0: eb 0e 66 66 2e WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:826 apply_returns (arch/x86/kernel/alternative.c:826 Put in a plain "ret" there so that gcc doesn't put a return thunk in in its place which special and gets checked. In addition: ERROR: modpost: "srso_alias_untrain_ret" [arch/x86/kvm/kvm-amd.ko] undefined! make[2]: *** [scripts/Makefile.modpost:145: Module.symvers] Chyba 1 make[1]: *** [/usr/src/linux-6.8.3/Makefile:1873: modpost] Chyba 2 make: *** [Makefile:240: __sub-make] Chyba 2 since !SRSO builds would use the dummy return thunk as reported by petr.pisar@atlas.cz, https://bugzilla.kernel.org/show_bug.cgi?id=218679. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202404020901.da75a60f-oliver.sang@intel.com Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/all/202404020901.da75a60f-oliver.sang@intel.com/ Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

x86/bugs: Fix the SRSO mitigation on Zen3/4

2024-04-10T14:19:43+00:00

Commit 4535e1a4174c4111d92c5a9a21e542d232e0fcaa upstream. The original version of the mitigation would patch in the calls to the untraining routines directly. That is, the alternative() in UNTRAIN_RET will patch in the CALL to srso_alias_untrain_ret() directly. However, even if commit e7c25c441e9e ("x86/cpu: Cleanup the untrain mess") meant well in trying to clean up the situation, due to micro- architectural reasons, the untraining routine srso_alias_untrain_ret() must be the target of a CALL instruction and not of a JMP instruction as it is done now. Reshuffle the alternative macros to accomplish that. Fixes: e7c25c441e9e ("x86/cpu: Cleanup the untrain mess") Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Ingo Molnar Cc: stable@kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

x86/lib: Fix overflow when counting digits

2024-01-25T22:52:32+00:00

[ Upstream commit a24d61c609813963aacc9f6ec8343f4fcaac7243 ] tl;dr: The num_digits() function has a theoretical overflow issue. But it doesn't affect any actual in-tree users. Fix it by using a larger type for one of the local variables. Long version: There is an overflow in variable m in function num_digits when val is >= 1410065408 which leads to the digit calculation loop to iterate more times than required. This results in either more digits being counted or in some cases (for example where val is 1932683193) the value of m eventually overflows to zero and the while loop spins forever). Currently the function num_digits is currently only being used for small values of val in the SMP boot stage for digit counting on the number of cpus and NUMA nodes, so the overflow is never encountered. However it is useful to fix the overflow issue in case the function is used for other purposes in the future. (The issue was discovered while investigating the digit counting performance in various kernel helper functions rather than any real-world use-case). The simplest fix is to make m a long long, the overhead in multiplication speed for a long long is very minor for small values of val less than 10000 on modern processors. The alternative fix is to replace the multiplication with a constant division by 10 loop (this compiles down to an multiplication and shift) without needing to make m a long long, but this is slightly slower than the fix in this commit when measured on a range of x86 processors). [ dhansen: subject and changelog tweaks ] Fixes: 646e29a1789a ("x86: Improve the printout of the SMP bootup CPU table") Signed-off-by: Colin Ian King Signed-off-by: Dave Hansen Link: https://lore.kernel.org/all/20231102174901.2590325-1-colin.i.king%40gmail.com Signed-off-by: Sasha Levin

iov_iter, x86: Be consistent about the __user tag on copy_mc_to_user()

2023-11-20T10:08:12+00:00

[ Upstream commit 066baf92bed934c9fb4bcee97a193f47aa63431c ] copy_mc_to_user() has the destination marked __user on powerpc, but not on x86; the latter results in a sparse warning in lib/iov_iter.c. Fix this by applying the tag on x86 too. Fixes: ec6347bb4339 ("x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()") Signed-off-by: David Howells Link: https://lore.kernel.org/r/20230925120309.1731676-3-dhowells@redhat.com cc: Dan Williams cc: Thomas Gleixner cc: Ingo Molnar cc: Borislav Petkov cc: Dave Hansen cc: "H. Peter Anvin" cc: Alexander Viro cc: Jens Axboe cc: Christoph Hellwig cc: Christian Brauner cc: Matthew Wilcox cc: Linus Torvalds cc: David Laight cc: x86@kernel.org cc: linux-block@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

x86/retpoline,kprobes: Fix position of thunk sections with CONFIG_LTO_CLANG

2023-08-26T12:23:40+00:00

commit 79cd2a11224eab86d6673fe8a11d2046ae9d2757 upstream. The linker script arch/x86/kernel/vmlinux.lds.S matches the thunk sections ".text.__x86.*" from arch/x86/lib/retpoline.S as follows: .text { [...] TEXT_TEXT [...] __indirect_thunk_start = .; *(.text.__x86.*) __indirect_thunk_end = .; [...] } Macro TEXT_TEXT references TEXT_MAIN which normally expands to only ".text". However, with CONFIG_LTO_CLANG, TEXT_MAIN becomes ".text .text.[0-9a-zA-Z_]*" which wrongly matches also the thunk sections. The output layout is then different than expected. For instance, the currently defined range [__indirect_thunk_start, __indirect_thunk_end] becomes empty. Prevent the problem by using ".." as the first separator, for example, ".text..__x86.indirect_thunk". This pattern is utilized by other explicit section names which start with one of the standard prefixes, such as ".text" or ".data", and that need to be individually selected in the linker script. [ nathan: Fix conflicts with SRSO and fold in fix issue brought up by Andrew Cooper in post-review: https://lore.kernel.org/20230803230323.1478869-1-andrew.cooper3@citrix.com ] Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO") Signed-off-by: Petr Pavlu Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Nathan Chancellor Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230711091952.27944-2-petr.pavlu@suse.com Signed-off-by: Greg Kroah-Hartman

x86/retpoline: Don't clobber RFLAGS during srso_safe_ret()

2023-08-26T12:23:40+00:00

commit ba5ca5e5e6a1d55923e88b4a83da452166f5560e upstream. Use LEA instead of ADD when adjusting %rsp in srso_safe_ret{,_alias}() so as to avoid clobbering flags. Drop one of the INT3 instructions to account for the LEA consuming one more byte than the ADD. KVM's emulator makes indirect calls into a jump table of sorts, where the destination of each call is a small blob of code that performs fast emulation by executing the target instruction with fixed operands. E.g. to emulate ADC, fastop() invokes adcb_al_dl(): adcb_al_dl: <+0>: adc %dl,%al <+2>: jmp <__x86_return_thunk> A major motivation for doing fast emulation is to leverage the CPU to handle consumption and manipulation of arithmetic flags, i.e. RFLAGS is both an input and output to the target of the call. fastop() collects the RFLAGS result by pushing RFLAGS onto the stack and popping them back into a variable (held in %rdi in this case): asm("push %[flags]; popf; " CALL_NOSPEC " ; pushf; pop %[flags]\n" <+71>: mov 0xc0(%r8),%rdx <+78>: mov 0x100(%r8),%rcx <+85>: push %rdi <+86>: popf <+87>: call *%rsi <+89>: nop <+90>: nop <+91>: nop <+92>: pushf <+93>: pop %rdi and then propagating the arithmetic flags into the vCPU's emulator state: ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK); <+64>: and $0xfffffffffffff72a,%r9 <+94>: and $0x8d5,%edi <+109>: or %rdi,%r9 <+122>: mov %r9,0x10(%r8) The failures can be most easily reproduced by running the "emulator" test in KVM-Unit-Tests. If you're feeling a bit of deja vu, see commit b63f20a778c8 ("x86/retpoline: Don't clobber RFLAGS during CALL_NOSPEC on i386"). In addition, this breaks booting of clang-compiled guest on a gcc-compiled host where the host contains the %rsp-modifying SRSO mitigations. [ bp: Massage commit message, extend, remove addresses. ] Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Closes: https://lore.kernel.org/all/de474347-122d-54cd-eabf-9dcc95ab9eae@amd.com Reported-by: Srikanth Aithal Reported-by: Nathan Chancellor Signed-off-by: Sean Christopherson Signed-off-by: Borislav Petkov (AMD) Tested-by: Nathan Chancellor Cc: stable@vger.kernel.org Link: https://lore.kernel.org/20230810013334.GA5354@dev-arch.thelio-3990X/ Link: https://lore.kernel.org/r/20230811155255.250835-1-seanjc@google.com Signed-off-by: Greg Kroah-Hartman