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Message-ID: <8a52b522-7b9d-e3d4-9c04-98292db11d85@redhat.com>
Date: Tue, 8 Jan 2019 10:04:28 +0100
From: David Hildenbrand <david@...hat.com>
To: Christophe Leroy <christophe.leroy@....fr>,
Kees Cook <keescook@...omium.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Mike Rapoport <rppt@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-mm@...ck.org
Subject: Re: [PATCH v2 2/2] powerpc: use probe_user_read()
On 08.01.19 08:37, Christophe Leroy wrote:
> Instead of opencoding, use probe_user_read() to failessly
> read a user location.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
> v2: Using probe_user_read() instead of probe_user_address()
>
> arch/powerpc/kernel/process.c | 12 +-----------
> arch/powerpc/mm/fault.c | 6 +-----
> arch/powerpc/perf/callchain.c | 20 +++-----------------
> arch/powerpc/perf/core-book3s.c | 8 +-------
> arch/powerpc/sysdev/fsl_pci.c | 10 ++++------
> 5 files changed, 10 insertions(+), 46 deletions(-)
>
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index ce393df243aa..6a4b59d574c2 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1298,16 +1298,6 @@ void show_user_instructions(struct pt_regs *regs)
>
> pc = regs->nip - (NR_INSN_TO_PRINT * 3 / 4 * sizeof(int));
>
> - /*
> - * Make sure the NIP points at userspace, not kernel text/data or
> - * elsewhere.
> - */
> - if (!__access_ok(pc, NR_INSN_TO_PRINT * sizeof(int), USER_DS)) {
> - pr_info("%s[%d]: Bad NIP, not dumping instructions.\n",
> - current->comm, current->pid);
> - return;
> - }
> -
> seq_buf_init(&s, buf, sizeof(buf));
>
> while (n) {
> @@ -1318,7 +1308,7 @@ void show_user_instructions(struct pt_regs *regs)
> for (i = 0; i < 8 && n; i++, n--, pc += sizeof(int)) {
> int instr;
>
> - if (probe_kernel_address((const void *)pc, instr)) {
> + if (probe_user_read(&instr, (void __user *)pc, sizeof(instr))) {
> seq_buf_printf(&s, "XXXXXXXX ");
> continue;
> }
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 887f11bcf330..ec74305fa330 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -276,12 +276,8 @@ static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
> if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) &&
> access_ok(nip, sizeof(*nip))) {
> unsigned int inst;
> - int res;
>
> - pagefault_disable();
> - res = __get_user_inatomic(inst, nip);
> - pagefault_enable();
> - if (!res)
> + if (!probe_user_read(&inst, nip, sizeof(inst)))
> return !store_updates_sp(inst);
> *must_retry = true;
> }
> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
> index 0af051a1974e..0680efb2237b 100644
> --- a/arch/powerpc/perf/callchain.c
> +++ b/arch/powerpc/perf/callchain.c
> @@ -159,12 +159,8 @@ static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
> ((unsigned long)ptr & 7))
> return -EFAULT;
>
> - pagefault_disable();
> - if (!__get_user_inatomic(*ret, ptr)) {
> - pagefault_enable();
> + if (!probe_user_read(ret, ptr, sizeof(*ret)))
> return 0;
> - }
> - pagefault_enable();
>
> return read_user_stack_slow(ptr, ret, 8);
> }
> @@ -175,12 +171,8 @@ static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> ((unsigned long)ptr & 3))
> return -EFAULT;
>
> - pagefault_disable();
> - if (!__get_user_inatomic(*ret, ptr)) {
> - pagefault_enable();
> + if (!probe_user_read(ret, ptr, sizeof(*ret)))
> return 0;
> - }
> - pagefault_enable();
>
> return read_user_stack_slow(ptr, ret, 4);
> }
> @@ -307,17 +299,11 @@ static inline int current_is_64bit(void)
> */
> static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> {
> - int rc;
> -
> if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
> ((unsigned long)ptr & 3))
> return -EFAULT;
>
> - pagefault_disable();
> - rc = __get_user_inatomic(*ret, ptr);
> - pagefault_enable();
> -
> - return rc;
> + return probe_user_read(ret, ptr, sizeof(*ret));
> }
>
> static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index b0723002a396..4b64ddf0db68 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -416,7 +416,6 @@ static void power_pmu_sched_task(struct perf_event_context *ctx, bool sched_in)
> static __u64 power_pmu_bhrb_to(u64 addr)
> {
> unsigned int instr;
> - int ret;
> __u64 target;
>
> if (is_kernel_addr(addr)) {
> @@ -427,13 +426,8 @@ static __u64 power_pmu_bhrb_to(u64 addr)
> }
>
> /* Userspace: need copy instruction here then translate it */
> - pagefault_disable();
> - ret = __get_user_inatomic(instr, (unsigned int __user *)addr);
> - if (ret) {
> - pagefault_enable();
> + if (probe_user_read(&instr, (unsigned int __user *)addr, sizeof(instr)))
> return 0;
> - }
> - pagefault_enable();
>
> target = branch_target(&instr);
> if ((!target) || (instr & BRANCH_ABSOLUTE))
> diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
> index 918be816b097..c8a1b26489f5 100644
> --- a/arch/powerpc/sysdev/fsl_pci.c
> +++ b/arch/powerpc/sysdev/fsl_pci.c
> @@ -1068,13 +1068,11 @@ int fsl_pci_mcheck_exception(struct pt_regs *regs)
> addr += mfspr(SPRN_MCAR);
>
> if (is_in_pci_mem_space(addr)) {
> - if (user_mode(regs)) {
> - pagefault_disable();
> - ret = get_user(inst, (__u32 __user *)regs->nip);
> - pagefault_enable();
> - } else {
> + if (user_mode(regs))
> + ret = probe_user_read(&inst, (void __user *)regs->nip,
> + sizeof(inst));
What about also adding probe_user_address ?
> + else
> ret = probe_kernel_address((void *)regs->nip, inst);
> - }
>
> if (!ret && mcheck_handle_load(regs, inst)) {
> regs->nip += 4;
>
--
Thanks,
David / dhildenb
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