From: Oleg Nesterov <oleg@redhat.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: mpe@ellerman.id.au, rostedt@goodmis.org, paulus@samba.org,
jniethe5@gmail.com, naveen.n.rao@linux.ibm.com,
sandipan@linux.ibm.com, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] powerpc/uprobes: Validation for prefixed instruction
Date: Sat, 6 Feb 2021 19:06:05 +0100 [thread overview]
Message-ID: <20210206180604.GA8897@redhat.com> (raw)
In-Reply-To: <20210204104703.273429-1-ravi.bangoria@linux.ibm.com>
On 02/04, Ravi Bangoria wrote:
>
> +static int get_instr(struct mm_struct *mm, unsigned long addr, u32 *instr)
> +{
> + struct page *page;
> + struct vm_area_struct *vma;
> + void *kaddr;
> + unsigned int gup_flags = FOLL_FORCE | FOLL_SPLIT_PMD;
> +
> + if (get_user_pages_remote(mm, addr, 1, gup_flags, &page, &vma, NULL) <= 0)
> + return -EINVAL;
"vma" is not used, and I don't think you need FOLL_SPLIT_PMD.
Otherwise I can't really comment this ppc-specific change.
To be honest, I don't even understand why do we need this fix. Sure, the
breakpoint in the middle of 64-bit insn won't work, why do we care? The
user should know what does he do.
Not to mention we can't really trust get_user_pages() in that this page
can be modified by mm owner or debugger...
But I won't argue.
Oleg.
WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org, rostedt@goodmis.org,
paulus@samba.org, sandipan@linux.ibm.com, jniethe5@gmail.com,
naveen.n.rao@linux.ibm.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powerpc/uprobes: Validation for prefixed instruction
Date: Sat, 6 Feb 2021 19:06:05 +0100 [thread overview]
Message-ID: <20210206180604.GA8897@redhat.com> (raw)
In-Reply-To: <20210204104703.273429-1-ravi.bangoria@linux.ibm.com>
On 02/04, Ravi Bangoria wrote:
>
> +static int get_instr(struct mm_struct *mm, unsigned long addr, u32 *instr)
> +{
> + struct page *page;
> + struct vm_area_struct *vma;
> + void *kaddr;
> + unsigned int gup_flags = FOLL_FORCE | FOLL_SPLIT_PMD;
> +
> + if (get_user_pages_remote(mm, addr, 1, gup_flags, &page, &vma, NULL) <= 0)
> + return -EINVAL;
"vma" is not used, and I don't think you need FOLL_SPLIT_PMD.
Otherwise I can't really comment this ppc-specific change.
To be honest, I don't even understand why do we need this fix. Sure, the
breakpoint in the middle of 64-bit insn won't work, why do we care? The
user should know what does he do.
Not to mention we can't really trust get_user_pages() in that this page
can be modified by mm owner or debugger...
But I won't argue.
Oleg.
next prev parent reply other threads:[~2021-02-06 18:07 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 10:47 [PATCH v2] powerpc/uprobes: Validation for prefixed instruction Ravi Bangoria
2021-02-04 10:47 ` Ravi Bangoria
2021-02-04 10:49 ` Ravi Bangoria
2021-02-04 10:49 ` Ravi Bangoria
2021-02-04 13:15 ` Naveen N. Rao
2021-02-04 13:15 ` Naveen N. Rao
2021-02-08 11:08 ` Ravi Bangoria
2021-02-08 11:08 ` Ravi Bangoria
2021-02-04 14:19 ` Ananth N Mavinakayanahalli
2021-02-04 13:08 ` Naveen N. Rao
2021-02-04 13:08 ` Naveen N. Rao
2021-02-04 16:12 ` Naveen N. Rao
2021-02-04 16:12 ` Naveen N. Rao
2021-02-08 11:10 ` Ravi Bangoria
2021-02-08 11:10 ` Ravi Bangoria
2021-02-08 11:13 ` Ravi Bangoria
2021-02-08 11:13 ` Ravi Bangoria
2021-02-06 18:06 ` Oleg Nesterov [this message]
2021-02-06 18:06 ` Oleg Nesterov
2021-02-08 11:06 ` Ravi Bangoria
2021-02-08 11:06 ` Ravi Bangoria
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