kernel.git/arch/arm64/kernel/ptrace.c, branch linux-rolling-stable

arm64: poe: fix stale POR_EL0 values for ptrace

2026-03-04T12:21:28Z

[ Upstream commit 1f3b950492db411e6c30ee0076b61ef2694c100a ] If a process wrote to POR_EL0 and then crashed before a context switch happened, the coredump would contain an incorrect value for POR_EL0. The value read in poe_get() would be a stale value left in thread.por_el0. Fix this by reading the value from the system register, if the target thread is the current thread. This matches what gcs/fpsimd do. Fixes: 175198199262 ("arm64/ptrace: add support for FEAT_POE") Reported-by: David Spickett Cc: stable@vger.kernel.org Signed-off-by: Joey Gouly Cc: Kevin Brodsky Cc: Mark Rutland Reviewed-by: Kevin Brodsky Acked-by: Mark Rutland Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

arm64/fpsimd: ptrace: Fix SVE writes on !SME systems

2026-01-22T10:10:23Z

When SVE is supported but SME is not supported, a ptrace write to the NT_ARM_SVE regset can place the tracee into an invalid state where (non-streaming) SVE register data is stored in FP_STATE_SVE format but TIF_SVE is clear. This can result in a later warning from fpsimd_restore_current_state(), e.g. WARNING: CPU: 0 PID: 7214 at arch/arm64/kernel/fpsimd.c:383 fpsimd_restore_current_state+0x50c/0x748 When this happens, fpsimd_restore_current_state() will set TIF_SVE, placing the task into the correct state. This occurs before any other check of TIF_SVE can possibly occur, as other checks of TIF_SVE only happen while the FPSIMD/SVE/SME state is live. Thus, aside from the warning, there is no functional issue. This bug was introduced during rework to error handling in commit: 9f8bf718f2923 ("arm64/fpsimd: ptrace: Gracefully handle errors") ... where the setting of TIF_SVE was moved into a block which is only executed when system_supports_sme() is true. Fix this by removing the system_supports_sme() check. This ensures that TIF_SVE is set for (SVE-formatted) writes to NT_ARM_SVE, at the cost of unconditionally manipulating the tracee's saved svcr value. The manipulation of svcr is benign and inexpensive, and we already do similar elsewhere (e.g. during signal handling), so I don't think it's worth guarding this with system_supports_sme() checks. Aside from the above, there is no functional change. The 'type' argument to sve_set_common() is only set to ARM64_VEC_SME (in ssve_set())) when system_supports_sme(), so the ARM64_VEC_SME case in the switch statement is still unreachable when !system_supports_sme(). When CONFIG_ARM64_SME=n, the only caller of sve_set_common() is sve_set(), and the compiler can constant-fold for the case where type is ARM64_VEC_SVE, removing the logic for other cases. Reported-by: syzbot+d4ab35af21e99d07ce67@syzkaller.appspotmail.com Fixes: 9f8bf718f292 ("arm64/fpsimd: ptrace: Gracefully handle errors") Signed-off-by: Mark Rutland Cc: Cc: Mark Brown Cc: Will Deacon Reviewed-by: Mark Brown Signed-off-by: Catalin Marinas

arm64/sme: Support disabling streaming mode via ptrace on SME only systems

2025-11-17T20:11:54Z

Currently it is not possible to disable streaming mode via ptrace on SME only systems, the interface for doing this is to write via NT_ARM_SVE but such writes will be rejected on a system without SVE support. Enable this functionality by allowing userspace to write SVE_PT_REGS_FPSIMD format data via NT_ARM_SVE with the vector length set to 0 on SME only systems. Such writes currently error since we require that a vector length is specified which should minimise the risk that existing software is relying on current behaviour. Reads are not supported since I am not aware of any use case for this and there is some risk that an existing userspace application may be confused if it reads NT_ARM_SVE on a system without SVE. Existing kernels will return FPSIMD formatted register state from NT_ARM_SVE if full SVE state is not stored, for example if the task has not used SVE. Returning a vector length of 0 would create a risk that software would try to do things like allocate space for register state with zero sizes, while returning a vector length of 128 bits would look like SVE is supported. It seems safer to just not make the changes to add read support. It remains possible for userspace to detect a SME only system via the ptrace interface only since reads of NT_ARM_SSVE and NT_ARM_ZA will succeed while reads of NT_ARM_SVE will fail. Read/write access to the FPSIMD registers in non-streaming mode is available via REGSET_FPR. sve_set_common() already avoids allocating SVE storage when doing a FPSIMD formatted write and allocating SME storage when doing a NT_ARM_SVE write so we change the function to validate the new case and skip setting a vector length for it. The aim is to make a minimally invasive change, no operation that would previously have succeeded will be affected, and we use a previously defined interface in new circumstances rather than define completely new ABI. Signed-off-by: Mark Brown Reviewed-by: David Spickett Signed-off-by: Catalin Marinas

Merge tag 'execve-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

2025-07-29T00:11:40Z

Pull execve updates from Kees Cook: - Introduce regular REGSET note macros arch-wide (Dave Martin) - Remove arbitrary 4K limitation of program header size (Yin Fengwei) - Reorder function qualifiers for copy_clone_args_from_user() (Dishank Jogi) * tag 'execve-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (25 commits) fork: reorder function qualifiers for copy_clone_args_from_user binfmt_elf: remove the 4k limitation of program header size binfmt_elf: Warn on missing or suspicious regset note names xtensa: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names um: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names x86/ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names sparc: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names sh: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names s390/ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names riscv: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names powerpc/ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names parisc: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names openrisc: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names nios2: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names MIPS: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names m68k: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names LoongArch: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names hexagon: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names csky: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names arm64: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names ...

arm64: ptrace: Use USER_REGSET_NOTE_TYPE() to specify regset note names

2025-07-15T05:27:47Z

Instead of having the core code guess the note name for each regset, use USER_REGSET_NOTE_TYPE() to pick the correct name from elf.h. This does not affect the correctness of switch(note_type) and similar code, since note type values known to Linux for coredump purposes were already required to be unique. Signed-off-by: Dave Martin Cc: Catalin Marinas Cc: Will Deacon Cc: Oleg Nesterov Cc: Kees Cook Cc: Akihiko Odaki Cc: linux-arm-kernel@lists.infradead.org Reviewed-by: Akihiko Odaki Link: https://lore.kernel.org/r/20250701135616.29630-7-Dave.Martin@arm.com Signed-off-by: Kees Cook

arm64/ptrace: Fix stack-out-of-bounds read in regs_get_kernel_stack_nth()

2025-06-12T16:28:18Z

KASAN reports a stack-out-of-bounds read in regs_get_kernel_stack_nth(). Call Trace: [ 97.283505] BUG: KASAN: stack-out-of-bounds in regs_get_kernel_stack_nth+0xa8/0xc8 [ 97.284677] Read of size 8 at addr ffff800089277c10 by task 1.sh/2550 [ 97.285732] [ 97.286067] CPU: 7 PID: 2550 Comm: 1.sh Not tainted 6.6.0+ #11 [ 97.287032] Hardware name: linux,dummy-virt (DT) [ 97.287815] Call trace: [ 97.288279] dump_backtrace+0xa0/0x128 [ 97.288946] show_stack+0x20/0x38 [ 97.289551] dump_stack_lvl+0x78/0xc8 [ 97.290203] print_address_description.constprop.0+0x84/0x3c8 [ 97.291159] print_report+0xb0/0x280 [ 97.291792] kasan_report+0x84/0xd0 [ 97.292421] __asan_load8+0x9c/0xc0 [ 97.293042] regs_get_kernel_stack_nth+0xa8/0xc8 [ 97.293835] process_fetch_insn+0x770/0xa30 [ 97.294562] kprobe_trace_func+0x254/0x3b0 [ 97.295271] kprobe_dispatcher+0x98/0xe0 [ 97.295955] kprobe_breakpoint_handler+0x1b0/0x210 [ 97.296774] call_break_hook+0xc4/0x100 [ 97.297451] brk_handler+0x24/0x78 [ 97.298073] do_debug_exception+0xac/0x178 [ 97.298785] el1_dbg+0x70/0x90 [ 97.299344] el1h_64_sync_handler+0xcc/0xe8 [ 97.300066] el1h_64_sync+0x78/0x80 [ 97.300699] kernel_clone+0x0/0x500 [ 97.301331] __arm64_sys_clone+0x70/0x90 [ 97.302084] invoke_syscall+0x68/0x198 [ 97.302746] el0_svc_common.constprop.0+0x11c/0x150 [ 97.303569] do_el0_svc+0x38/0x50 [ 97.304164] el0_svc+0x44/0x1d8 [ 97.304749] el0t_64_sync_handler+0x100/0x130 [ 97.305500] el0t_64_sync+0x188/0x190 [ 97.306151] [ 97.306475] The buggy address belongs to stack of task 1.sh/2550 [ 97.307461] and is located at offset 0 in frame: [ 97.308257] __se_sys_clone+0x0/0x138 [ 97.308910] [ 97.309241] This frame has 1 object: [ 97.309873] [48, 184) 'args' [ 97.309876] [ 97.310749] The buggy address belongs to the virtual mapping at [ 97.310749] [ffff800089270000, ffff800089279000) created by: [ 97.310749] dup_task_struct+0xc0/0x2e8 [ 97.313347] [ 97.313674] The buggy address belongs to the physical page: [ 97.314604] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14f69a [ 97.315885] flags: 0x15ffffe00000000(node=1|zone=2|lastcpupid=0xfffff) [ 97.316957] raw: 015ffffe00000000 0000000000000000 dead000000000122 0000000000000000 [ 97.318207] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 [ 97.319445] page dumped because: kasan: bad access detected [ 97.320371] [ 97.320694] Memory state around the buggy address: [ 97.321511] ffff800089277b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 97.322681] ffff800089277b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 97.323846] >ffff800089277c00: 00 00 f1 f1 f1 f1 f1 f1 00 00 00 00 00 00 00 00 [ 97.325023] ^ [ 97.325683] ffff800089277c80: 00 00 00 00 00 00 00 00 00 f3 f3 f3 f3 f3 f3 f3 [ 97.326856] ffff800089277d00: f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 This issue seems to be related to the behavior of some gcc compilers and was also fixed on the s390 architecture before: commit d93a855c31b7 ("s390/ptrace: Avoid KASAN false positives in regs_get_kernel_stack_nth()") As described in that commit, regs_get_kernel_stack_nth() has confirmed that `addr` is on the stack, so reading the value at `*addr` should be allowed. Use READ_ONCE_NOCHECK() helper to silence the KASAN check for this case. Fixes: 0a8ea52c3eb1 ("arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature") Signed-off-by: Tengda Wu Link: https://lore.kernel.org/r/20250604005533.1278992-1-wutengda@huaweicloud.com [will: Use '*addr' as the argument to READ_ONCE_NOCHECK()] Signed-off-by: Will Deacon

arm64/fpsimd: ptrace: Gracefully handle errors

2025-05-08T14:29:11Z

Within sve_set_common() we do not handle error conditions correctly: * When writing to NT_ARM_SSVE, if sme_alloc() fails, the task will be left with task->thread.sme_state==NULL, but TIF_SME will be set and task->thread.fp_type==FP_STATE_SVE. This will result in a subsequent null pointer dereference when the task's state is loaded or otherwise manipulated. * When writing to NT_ARM_SSVE, if sve_alloc() fails, the task will be left with task->thread.sve_state==NULL, but TIF_SME will be set, PSTATE.SM will be set, and task->thread.fp_type==FP_STATE_FPSIMD. This is not a legitimate state, and can result in various problems, including a subsequent null pointer dereference and/or the task inheriting stale streaming mode register state the next time its state is loaded into hardware. * When writing to NT_ARM_SSVE, if the VL is changed but the resulting VL differs from that in the header, the task will be left with TIF_SME set, PSTATE.SM set, but task->thread.fp_type==FP_STATE_FPSIMD. This is not a legitimate state, and can result in various problems as described above. Avoid these problems by allocating memory earlier, and by changing the task's saved fp_type to FP_STATE_SVE before skipping register writes due to a change of VL. To make early returns simpler, I've moved the call to fpsimd_flush_task_state() earlier. As the tracee's state has already been saved, and the tracee is known to be blocked for the duration of sve_set_common(), it doesn't matter whether this is called at the start or the end. For consistency I've moved the setting of TIF_SVE earlier. This will be cleared when loading FPSIMD-only state, and so moving this has no resulting functional change. Note that we only allocate the memory for SVE state when SVE register contents are provided, avoiding unnecessary memory allocations for tasks which only use FPSIMD. Fixes: e12310a0d30f ("arm64/sme: Implement ptrace support for streaming mode SVE registers") Fixes: baa8515281b3 ("arm64/fpsimd: Track the saved FPSIMD state type separately to TIF_SVE") Fixes: 5d0a8d2fba50 ("arm64/ptrace: Ensure that SME is set up for target when writing SSVE state") Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: David Spickett Cc: Luis Machado Cc: Marc Zyngier Cc: Mark Brown Cc: Will Deacon Link: https://lore.kernel.org/r/20250508132644.1395904-20-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64/fpsimd: ptrace: Mandate SVE payload for streaming-mode state

2025-05-08T14:29:11Z

When a task has PSTATE.SM==1, reads of NT_ARM_SSVE are required to always present a header with SVE_PT_REGS_SVE, and register data in SVE format. Reads of NT_ARM_SSVE must never present register data in FPSIMD format. Within the kernel, we always expect streaming SVE data to be stored in SVE format. Currently a user can write to NT_ARM_SSVE with a header presenting SVE_PT_REGS_FPSIMD rather than SVE_PT_REGS_SVE, placing the task's FPSIMD/SVE data into an invalid state. To fix this we can either: (a) Forbid such writes. (b) Accept such writes, and immediately convert data into SVE format. Take the simple option and forbid such writes. Fixes: e12310a0d30f ("arm64/sme: Implement ptrace support for streaming mode SVE registers") Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: David Spickett Cc: Luis Machado Cc: Marc Zyngier Cc: Mark Brown Cc: Will Deacon Reviewed-by: Mark Brown Link: https://lore.kernel.org/r/20250508132644.1395904-19-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64/fpsimd: ptrace: Do not present register data for inactive mode

2025-05-08T14:29:11Z

The SME ptrace ABI is written around the incorrect assumption that SVE_PT_REGS_FPSIMD and SVE_PT_REGS_SVE are independent bit flags, where it is possible for both to be clear. In reality they are different values for bit 0 of the header flags, where SVE_PT_REGS_FPSIMD is 0 and SVE_PT_REGS_SVE is 1. In cases where code was written expecting that neither bit flag would be set, the value is equivalent to SVE_PT_REGS_FPSIMD. One consequence of this is that reads of the NT_ARM_SVE or NT_ARM_SSVE will erroneously present data from the other mode: * When PSTATE.SM==1, reads of NT_ARM_SVE will present a header with SVE_PT_REGS_FPSIMD, and FPSIMD-formatted data from streaming mode. * When PSTATE.SM==0, reads of NT_ARM_SSVE will present a header with SVE_PT_REGS_FPSIMD, and FPSIMD-formatted data from non-streaming mode. The original intent was that no register data would be provided in these cases, as described in commit: e12310a0d30f ("arm64/sme: Implement ptrace support for streaming mode SVE registers") Luckily, debuggers do not consume the bogus register data. Both GDB and LLDB read the NT_ARM_SSVE regset before the NT_ARM_SVE regset, and assume that when the NT_ARM_SSVE header presents SVE_PT_REGS_FPSIMD, it is necessary to read register contents from the NT_ARM_SVE regset, regardless of whether the NT_ARM_SSVE regset provided bogus register data. Fix the code to stop presenting register data from the inactive mode. At the same time, make the manipulation of the flag clearer, and remove the bogus comment from sve_set_common(). I've given this a quick spin with GDB and LLDB, and both seem happy. Fixes: e12310a0d30f ("arm64/sme: Implement ptrace support for streaming mode SVE registers") Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: David Spickett Cc: Luis Machado Cc: Marc Zyngier Cc: Mark Brown Cc: Will Deacon Link: https://lore.kernel.org/r/20250508132644.1395904-18-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64/fpsimd: ptrace: Save task state before generating SVE header

2025-05-08T14:29:11Z

As sve_init_header_from_task() consumes the saved value of PSTATE.SM and the saved fp_type, both must be saved before the header is generated. When generating a coredump for the current task, sve_get_common() calls sve_init_header_from_task() before saving the task's state. Consequently the header may be bogus, and the contents of the regset may be misleading. Fix this by saving the task's state before generting the header. Fixes: e12310a0d30f ("arm64/sme: Implement ptrace support for streaming mode SVE registers") Fixes: b017a0cea627 ("arm64/ptrace: Use saved floating point state type to determine SVE layout") Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: David Spickett Cc: Luis Machado Cc: Marc Zyngier Cc: Mark Brown Cc: Will Deacon Link: https://lore.kernel.org/r/20250508132644.1395904-17-mark.rutland@arm.com Signed-off-by: Will Deacon