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android_kernel_xiaomi_sm8450/arch/powerpc/kernel/ptrace/ptrace.c
Michael Ellerman 3be74fc0af powerpc/32: Fix overread/overwrite of thread_struct via ptrace 
commit 8e1278444446fc97778a5e5c99bca1ce0bbc5ec9 upstream.

The ptrace PEEKUSR/POKEUSR (aka PEEKUSER/POKEUSER) API allows a process
to read/write registers of another process.

To get/set a register, the API takes an index into an imaginary address
space called the "USER area", where the registers of the process are
laid out in some fashion.

The kernel then maps that index to a particular register in its own data
structures and gets/sets the value.

The API only allows a single machine-word to be read/written at a time.
So 4 bytes on 32-bit kernels and 8 bytes on 64-bit kernels.

The way floating point registers (FPRs) are addressed is somewhat
complicated, because double precision float values are 64-bit even on
32-bit CPUs. That means on 32-bit kernels each FPR occupies two
word-sized locations in the USER area. On 64-bit kernels each FPR
occupies one word-sized location in the USER area.

Internally the kernel stores the FPRs in an array of u64s, or if VSX is
enabled, an array of pairs of u64s where one half of each pair stores
the FPR. Which half of the pair stores the FPR depends on the kernel's
endianness.

To handle the different layouts of the FPRs depending on VSX/no-VSX and
big/little endian, the TS_FPR() macro was introduced.

Unfortunately the TS_FPR() macro does not take into account the fact
that the addressing of each FPR differs between 32-bit and 64-bit
kernels. It just takes the index into the "USER area" passed from
userspace and indexes into the fp_state.fpr array.

On 32-bit there are 64 indexes that address FPRs, but only 32 entries in
the fp_state.fpr array, meaning the user can read/write 256 bytes past
the end of the array. Because the fp_state sits in the middle of the
thread_struct there are various fields than can be overwritten,
including some pointers. As such it may be exploitable.

It has also been observed to cause systems to hang or otherwise
misbehave when using gdbserver, and is probably the root cause of this
report which could not be easily reproduced:
  https://lore.kernel.org/linuxppc-dev/dc38afe9-6b78-f3f5-666b-986939e40fc6@keymile.com/

Rather than trying to make the TS_FPR() macro even more complicated to
fix the bug, or add more macros, instead add a special-case for 32-bit
kernels. This is more obvious and hopefully avoids a similar bug
happening again in future.

Note that because 32-bit kernels never have VSX enabled the code doesn't
need to consider TS_FPRWIDTH/OFFSET at all. Add a BUILD_BUG_ON() to
ensure that 32-bit && VSX is never enabled.

Fixes: 87fec0514f ("powerpc: PTRACE_PEEKUSR/PTRACE_POKEUSER of FPR registers in little endian builds")
Cc: stable@vger.kernel.org # v3.13+
Reported-by: Ariel Miculas <ariel.miculas@belden.com>
Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220609133245.573565-1-mpe@ellerman.id.au
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-06-14 18:32:46 +02:00

495 lines
13 KiB
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/*
* PowerPC version
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
*
* Derived from "arch/m68k/kernel/ptrace.c"
* Copyright (C) 1994 by Hamish Macdonald
* Taken from linux/kernel/ptrace.c and modified for M680x0.
* linux/kernel/ptrace.c is by Ross Biro 1/23/92, edited by Linus Torvalds
*
* Modified by Cort Dougan (cort@hq.fsmlabs.com)
* and Paul Mackerras (paulus@samba.org).
*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file README.legal in the main directory of
* this archive for more details.
*/
#include <linux/regset.h>
#include <linux/tracehook.h>
#include <linux/audit.h>
#include <linux/context_tracking.h>
#include <linux/syscalls.h>
#include <asm/switch_to.h>
#include <asm/asm-prototypes.h>
#include <asm/debug.h>
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
#include "ptrace-decl.h"
/*
* Called by kernel/ptrace.c when detaching..
*
* Make sure single step bits etc are not set.
*/
void ptrace_disable(struct task_struct *child)
{
/* make sure the single step bit is not set. */
user_disable_single_step(child);
}
long arch_ptrace(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
int ret = -EPERM;
void __user *datavp = (void __user *) data;
unsigned long __user *datalp = datavp;
switch (request) {
/* read the word at location addr in the USER area. */
case PTRACE_PEEKUSR: {
unsigned long index, tmp;
ret = -EIO;
/* convert to index and check */
#ifdef CONFIG_PPC32
index = addr >> 2;
if ((addr & 3) || (index > PT_FPSCR)
|| (child->thread.regs == NULL))
#else
index = addr >> 3;
if ((addr & 7) || (index > PT_FPSCR))
#endif
break;
CHECK_FULL_REGS(child->thread.regs);
if (index < PT_FPR0) {
ret = ptrace_get_reg(child, (int) index, &tmp);
if (ret)
break;
} else {
unsigned int fpidx = index - PT_FPR0;
flush_fp_to_thread(child);
if (fpidx < (PT_FPSCR - PT_FPR0))
if (IS_ENABLED(CONFIG_PPC32)) {
// On 32-bit the index we are passed refers to 32-bit words
tmp = ((u32 *)child->thread.fp_state.fpr)[fpidx];
} else {
memcpy(&tmp, &child->thread.TS_FPR(fpidx),
sizeof(long));
}
else
tmp = child->thread.fp_state.fpscr;
}
ret = put_user(tmp, datalp);
break;
}
/* write the word at location addr in the USER area */
case PTRACE_POKEUSR: {
unsigned long index;
ret = -EIO;
/* convert to index and check */
#ifdef CONFIG_PPC32
index = addr >> 2;
if ((addr & 3) || (index > PT_FPSCR)
|| (child->thread.regs == NULL))
#else
index = addr >> 3;
if ((addr & 7) || (index > PT_FPSCR))
#endif
break;
CHECK_FULL_REGS(child->thread.regs);
if (index < PT_FPR0) {
ret = ptrace_put_reg(child, index, data);
} else {
unsigned int fpidx = index - PT_FPR0;
flush_fp_to_thread(child);
if (fpidx < (PT_FPSCR - PT_FPR0))
if (IS_ENABLED(CONFIG_PPC32)) {
// On 32-bit the index we are passed refers to 32-bit words
((u32 *)child->thread.fp_state.fpr)[fpidx] = data;
} else {
memcpy(&child->thread.TS_FPR(fpidx), &data,
sizeof(long));
}
else
child->thread.fp_state.fpscr = data;
ret = 0;
}
break;
}
case PPC_PTRACE_GETHWDBGINFO: {
struct ppc_debug_info dbginfo;
ppc_gethwdinfo(&dbginfo);
if (copy_to_user(datavp, &dbginfo,
sizeof(struct ppc_debug_info)))
return -EFAULT;
return 0;
}
case PPC_PTRACE_SETHWDEBUG: {
struct ppc_hw_breakpoint bp_info;
if (copy_from_user(&bp_info, datavp,
sizeof(struct ppc_hw_breakpoint)))
return -EFAULT;
return ppc_set_hwdebug(child, &bp_info);
}
case PPC_PTRACE_DELHWDEBUG: {
ret = ppc_del_hwdebug(child, data);
break;
}
case PTRACE_GET_DEBUGREG:
ret = ptrace_get_debugreg(child, addr, datalp);
break;
case PTRACE_SET_DEBUGREG:
ret = ptrace_set_debugreg(child, addr, data);
break;
#ifdef CONFIG_PPC64
case PTRACE_GETREGS64:
#endif
case PTRACE_GETREGS: /* Get all pt_regs from the child. */
return copy_regset_to_user(child, &user_ppc_native_view,
REGSET_GPR,
0, sizeof(struct user_pt_regs),
datavp);
#ifdef CONFIG_PPC64
case PTRACE_SETREGS64:
#endif
case PTRACE_SETREGS: /* Set all gp regs in the child. */
return copy_regset_from_user(child, &user_ppc_native_view,
REGSET_GPR,
0, sizeof(struct user_pt_regs),
datavp);
case PTRACE_GETFPREGS: /* Get the child FPU state (FPR0...31 + FPSCR) */
return copy_regset_to_user(child, &user_ppc_native_view,
REGSET_FPR,
0, sizeof(elf_fpregset_t),
datavp);
case PTRACE_SETFPREGS: /* Set the child FPU state (FPR0...31 + FPSCR) */
return copy_regset_from_user(child, &user_ppc_native_view,
REGSET_FPR,
0, sizeof(elf_fpregset_t),
datavp);
#ifdef CONFIG_ALTIVEC
case PTRACE_GETVRREGS:
return copy_regset_to_user(child, &user_ppc_native_view,
REGSET_VMX,
0, (33 * sizeof(vector128) +
sizeof(u32)),
datavp);
case PTRACE_SETVRREGS:
return copy_regset_from_user(child, &user_ppc_native_view,
REGSET_VMX,
0, (33 * sizeof(vector128) +
sizeof(u32)),
datavp);
#endif
#ifdef CONFIG_VSX
case PTRACE_GETVSRREGS:
return copy_regset_to_user(child, &user_ppc_native_view,
REGSET_VSX,
0, 32 * sizeof(double),
datavp);
case PTRACE_SETVSRREGS:
return copy_regset_from_user(child, &user_ppc_native_view,
REGSET_VSX,
0, 32 * sizeof(double),
datavp);
#endif
#ifdef CONFIG_SPE
case PTRACE_GETEVRREGS:
/* Get the child spe register state. */
return copy_regset_to_user(child, &user_ppc_native_view,
REGSET_SPE, 0, 35 * sizeof(u32),
datavp);
case PTRACE_SETEVRREGS:
/* Set the child spe register state. */
return copy_regset_from_user(child, &user_ppc_native_view,
REGSET_SPE, 0, 35 * sizeof(u32),
datavp);
#endif
default:
ret = ptrace_request(child, request, addr, data);
break;
}
return ret;
}
#ifdef CONFIG_SECCOMP
static int do_seccomp(struct pt_regs *regs)
{
if (!test_thread_flag(TIF_SECCOMP))
return 0;
/*
* The ABI we present to seccomp tracers is that r3 contains
* the syscall return value and orig_gpr3 contains the first
* syscall parameter. This is different to the ptrace ABI where
* both r3 and orig_gpr3 contain the first syscall parameter.
*/
regs->gpr[3] = -ENOSYS;
/*
* We use the __ version here because we have already checked
* TIF_SECCOMP. If this fails, there is nothing left to do, we
* have already loaded -ENOSYS into r3, or seccomp has put
* something else in r3 (via SECCOMP_RET_ERRNO/TRACE).
*/
if (__secure_computing(NULL))
return -1;
/*
* The syscall was allowed by seccomp, restore the register
* state to what audit expects.
* Note that we use orig_gpr3, which means a seccomp tracer can
* modify the first syscall parameter (in orig_gpr3) and also
* allow the syscall to proceed.
*/
regs->gpr[3] = regs->orig_gpr3;
return 0;
}
#else
static inline int do_seccomp(struct pt_regs *regs) { return 0; }
#endif /* CONFIG_SECCOMP */
/**
* do_syscall_trace_enter() - Do syscall tracing on kernel entry.
* @regs: the pt_regs of the task to trace (current)
*
* Performs various types of tracing on syscall entry. This includes seccomp,
* ptrace, syscall tracepoints and audit.
*
* The pt_regs are potentially visible to userspace via ptrace, so their
* contents is ABI.
*
* One or more of the tracers may modify the contents of pt_regs, in particular
* to modify arguments or even the syscall number itself.
*
* It's also possible that a tracer can choose to reject the system call. In
* that case this function will return an illegal syscall number, and will put
* an appropriate return value in regs->r3.
*
* Return: the (possibly changed) syscall number.
*/
long do_syscall_trace_enter(struct pt_regs *regs)
{
u32 flags;
user_exit();
flags = READ_ONCE(current_thread_info()->flags) &
(_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE);
if (flags) {
int rc = tracehook_report_syscall_entry(regs);
if (unlikely(flags & _TIF_SYSCALL_EMU)) {
/*
* A nonzero return code from
* tracehook_report_syscall_entry() tells us to prevent
* the syscall execution, but we are not going to
* execute it anyway.
*
* Returning -1 will skip the syscall execution. We want
* to avoid clobbering any registers, so we don't goto
* the skip label below.
*/
return -1;
}
if (rc) {
/*
* The tracer decided to abort the syscall. Note that
* the tracer may also just change regs->gpr[0] to an
* invalid syscall number, that is handled below on the
* exit path.
*/
goto skip;
}
}
/* Run seccomp after ptrace; allow it to set gpr[3]. */
if (do_seccomp(regs))
return -1;
/* Avoid trace and audit when syscall is invalid. */
if (regs->gpr[0] >= NR_syscalls)
goto skip;
if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_enter(regs, regs->gpr[0]);
if (!is_32bit_task())
audit_syscall_entry(regs->gpr[0], regs->gpr[3], regs->gpr[4],
regs->gpr[5], regs->gpr[6]);
else
audit_syscall_entry(regs->gpr[0],
regs->gpr[3] & 0xffffffff,
regs->gpr[4] & 0xffffffff,
regs->gpr[5] & 0xffffffff,
regs->gpr[6] & 0xffffffff);
/* Return the possibly modified but valid syscall number */
return regs->gpr[0];
skip:
/*
* If we are aborting explicitly, or if the syscall number is
* now invalid, set the return value to -ENOSYS.
*/
regs->gpr[3] = -ENOSYS;
return -1;
}
void do_syscall_trace_leave(struct pt_regs *regs)
{
int step;
audit_syscall_exit(regs);
if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_exit(regs, regs->result);
step = test_thread_flag(TIF_SINGLESTEP);
if (step || test_thread_flag(TIF_SYSCALL_TRACE))
tracehook_report_syscall_exit(regs, step);
user_enter();
}
void __init pt_regs_check(void);
/*
* Dummy function, its purpose is to break the build if struct pt_regs and
* struct user_pt_regs don't match.
*/
void __init pt_regs_check(void)
{
BUILD_BUG_ON(offsetof(struct pt_regs, gpr) !=
offsetof(struct user_pt_regs, gpr));
BUILD_BUG_ON(offsetof(struct pt_regs, nip) !=
offsetof(struct user_pt_regs, nip));
BUILD_BUG_ON(offsetof(struct pt_regs, msr) !=
offsetof(struct user_pt_regs, msr));
BUILD_BUG_ON(offsetof(struct pt_regs, msr) !=
offsetof(struct user_pt_regs, msr));
BUILD_BUG_ON(offsetof(struct pt_regs, orig_gpr3) !=
offsetof(struct user_pt_regs, orig_gpr3));
BUILD_BUG_ON(offsetof(struct pt_regs, ctr) !=
offsetof(struct user_pt_regs, ctr));
BUILD_BUG_ON(offsetof(struct pt_regs, link) !=
offsetof(struct user_pt_regs, link));
BUILD_BUG_ON(offsetof(struct pt_regs, xer) !=
offsetof(struct user_pt_regs, xer));
BUILD_BUG_ON(offsetof(struct pt_regs, ccr) !=
offsetof(struct user_pt_regs, ccr));
#ifdef __powerpc64__
BUILD_BUG_ON(offsetof(struct pt_regs, softe) !=
offsetof(struct user_pt_regs, softe));
#else
BUILD_BUG_ON(offsetof(struct pt_regs, mq) !=
offsetof(struct user_pt_regs, mq));
#endif
BUILD_BUG_ON(offsetof(struct pt_regs, trap) !=
offsetof(struct user_pt_regs, trap));
BUILD_BUG_ON(offsetof(struct pt_regs, dar) !=
offsetof(struct user_pt_regs, dar));
BUILD_BUG_ON(offsetof(struct pt_regs, dsisr) !=
offsetof(struct user_pt_regs, dsisr));
BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
offsetof(struct user_pt_regs, result));
BUILD_BUG_ON(sizeof(struct user_pt_regs) > sizeof(struct pt_regs));
// Now check that the pt_regs offsets match the uapi #defines
#define CHECK_REG(_pt, _reg) \
BUILD_BUG_ON(_pt != (offsetof(struct user_pt_regs, _reg) / \
sizeof(unsigned long)));
CHECK_REG(PT_R0, gpr[0]);
CHECK_REG(PT_R1, gpr[1]);
CHECK_REG(PT_R2, gpr[2]);
CHECK_REG(PT_R3, gpr[3]);
CHECK_REG(PT_R4, gpr[4]);
CHECK_REG(PT_R5, gpr[5]);
CHECK_REG(PT_R6, gpr[6]);
CHECK_REG(PT_R7, gpr[7]);
CHECK_REG(PT_R8, gpr[8]);
CHECK_REG(PT_R9, gpr[9]);
CHECK_REG(PT_R10, gpr[10]);
CHECK_REG(PT_R11, gpr[11]);
CHECK_REG(PT_R12, gpr[12]);
CHECK_REG(PT_R13, gpr[13]);
CHECK_REG(PT_R14, gpr[14]);
CHECK_REG(PT_R15, gpr[15]);
CHECK_REG(PT_R16, gpr[16]);
CHECK_REG(PT_R17, gpr[17]);
CHECK_REG(PT_R18, gpr[18]);
CHECK_REG(PT_R19, gpr[19]);
CHECK_REG(PT_R20, gpr[20]);
CHECK_REG(PT_R21, gpr[21]);
CHECK_REG(PT_R22, gpr[22]);
CHECK_REG(PT_R23, gpr[23]);
CHECK_REG(PT_R24, gpr[24]);
CHECK_REG(PT_R25, gpr[25]);
CHECK_REG(PT_R26, gpr[26]);
CHECK_REG(PT_R27, gpr[27]);
CHECK_REG(PT_R28, gpr[28]);
CHECK_REG(PT_R29, gpr[29]);
CHECK_REG(PT_R30, gpr[30]);
CHECK_REG(PT_R31, gpr[31]);
CHECK_REG(PT_NIP, nip);
CHECK_REG(PT_MSR, msr);
CHECK_REG(PT_ORIG_R3, orig_gpr3);
CHECK_REG(PT_CTR, ctr);
CHECK_REG(PT_LNK, link);
CHECK_REG(PT_XER, xer);
CHECK_REG(PT_CCR, ccr);
#ifdef CONFIG_PPC64
CHECK_REG(PT_SOFTE, softe);
#else
CHECK_REG(PT_MQ, mq);
#endif
CHECK_REG(PT_TRAP, trap);
CHECK_REG(PT_DAR, dar);
CHECK_REG(PT_DSISR, dsisr);
CHECK_REG(PT_RESULT, result);
#undef CHECK_REG
BUILD_BUG_ON(PT_REGS_COUNT != sizeof(struct user_pt_regs) / sizeof(unsigned long));
/*
* PT_DSCR isn't a real reg, but it's important that it doesn't overlap the
* real registers.
*/
BUILD_BUG_ON(PT_DSCR < sizeof(struct user_pt_regs) / sizeof(unsigned long));
// ptrace_get/put_fpr() rely on PPC32 and VSX being incompatible
BUILD_BUG_ON(IS_ENABLED(CONFIG_PPC32) && IS_ENABLED(CONFIG_VSX));
}
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