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65896545b6
When the hardend usercopy support was added for arm64, it was
concluded that all cases of usercopy into and out of thread_struct
were statically sized and so didn't require explicit whitelisting
of the appropriate fields in thread_struct.
Testing with usercopy hardening enabled has revealed that this is
not the case for certain ptrace regset manipulation calls on arm64.
This occurs because the sizes of usercopies associated with the
regset API are dynamic by construction, and because arm64 does not
always stage such copies via the stack: indeed the regset API is
designed to avoid the need for that by adding some bounds checking.
This is currently believed to affect only the fpsimd and TLS
registers.
Because the whitelisted fields in thread_struct must be contiguous,
this patch groups them together in a nested struct. It is also
necessary to be able to determine the location and size of that
struct, so rather than making the struct anonymous (which would
save on edits elsewhere) or adding an anonymous union containing
named and unnamed instances of the same struct (gross), this patch
gives the struct a name and makes the necessary edits to code that
references it (noisy but simple).
Care is needed to ensure that the new struct does not contain
padding (which the usercopy hardening would fail to protect).
For this reason, the presence of tp2_value is made unconditional,
since a padding field would be needed there in any case. This pads
up to the 16-byte alignment required by struct user_fpsimd_state.
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 9e8084d3f7 ("arm64: Implement thread_struct whitelist for hardened usercopy")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
124 lines
3.3 KiB
C
124 lines
3.3 KiB
C
/*
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* Based on arch/arm/kernel/sys_arm.c
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*
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* Copyright (C) People who wrote linux/arch/i386/kernel/sys_i386.c
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* Copyright (C) 1995, 1996 Russell King.
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* Copyright (C) 2012 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/compat.h>
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#include <linux/personality.h>
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#include <linux/sched.h>
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#include <linux/sched/signal.h>
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#include <linux/slab.h>
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#include <linux/syscalls.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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#include <asm/system_misc.h>
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#include <asm/unistd.h>
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static long
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__do_compat_cache_op(unsigned long start, unsigned long end)
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{
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long ret;
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do {
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unsigned long chunk = min(PAGE_SIZE, end - start);
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if (fatal_signal_pending(current))
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return 0;
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ret = __flush_cache_user_range(start, start + chunk);
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if (ret)
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return ret;
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cond_resched();
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start += chunk;
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} while (start < end);
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return 0;
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}
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static inline long
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do_compat_cache_op(unsigned long start, unsigned long end, int flags)
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{
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if (end < start || flags)
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return -EINVAL;
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if (!access_ok(VERIFY_READ, (const void __user *)start, end - start))
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return -EFAULT;
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return __do_compat_cache_op(start, end);
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}
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/*
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* Handle all unrecognised system calls.
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*/
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long compat_arm_syscall(struct pt_regs *regs)
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{
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siginfo_t info;
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unsigned int no = regs->regs[7];
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switch (no) {
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/*
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* Flush a region from virtual address 'r0' to virtual address 'r1'
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* _exclusive_. There is no alignment requirement on either address;
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* user space does not need to know the hardware cache layout.
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*
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* r2 contains flags. It should ALWAYS be passed as ZERO until it
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* is defined to be something else. For now we ignore it, but may
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* the fires of hell burn in your belly if you break this rule. ;)
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*
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* (at a later date, we may want to allow this call to not flush
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* various aspects of the cache. Passing '0' will guarantee that
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* everything necessary gets flushed to maintain consistency in
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* the specified region).
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*/
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case __ARM_NR_compat_cacheflush:
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return do_compat_cache_op(regs->regs[0], regs->regs[1], regs->regs[2]);
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case __ARM_NR_compat_set_tls:
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current->thread.uw.tp_value = regs->regs[0];
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/*
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* Protect against register corruption from context switch.
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* See comment in tls_thread_flush.
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*/
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barrier();
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write_sysreg(regs->regs[0], tpidrro_el0);
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return 0;
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default:
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/*
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* Calls 9f00xx..9f07ff are defined to return -ENOSYS
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* if not implemented, rather than raising SIGILL. This
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* way the calling program can gracefully determine whether
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* a feature is supported.
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*/
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if ((no & 0xffff) <= 0x7ff)
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return -ENOSYS;
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break;
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}
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info.si_signo = SIGILL;
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info.si_errno = 0;
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info.si_code = ILL_ILLTRP;
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info.si_addr = (void __user *)instruction_pointer(regs) -
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(compat_thumb_mode(regs) ? 2 : 4);
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arm64_notify_die("Oops - bad compat syscall(2)", regs, &info, no);
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return 0;
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}
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