From: Al Viro <viro@zeniv.linux.org.uk>
To: Jann Horn <jannh@google.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
linux-sparse@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
the arch/x86 maintainers <x86@kernel.org>,
kernel list <linux-kernel@vger.kernel.org>,
Qiaowei Ren <qiaowei.ren@intel.com>
Subject: Re: [PATCH v2 3/4] x86/fpu: Fix __user annotations
Date: Fri, 29 Mar 2019 19:42:08 +0000 [thread overview]
Message-ID: <20190329194208.GE2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAG48ez2+AeBuJ8i8RKL3THc1Nq1_vPyqLTXep8CvJgqVtGYCig@mail.gmail.com>
On Fri, Mar 29, 2019 at 08:25:25PM +0100, Jann Horn wrote:
> Oooh, it's a sparse bug.
It's *not* a bug.
> Apparently it's significant that the user pointer is stored as a
> __u64, and __u64 is defined as unsigned long long.
Yes, it is. Casts to uintptr_t (== unsigned long on all targets)
are OK; any other arithmetical type gives a warning, and quite
deliberately so.
Don't do it. If you want to say "I'm converting it to integer,
all traces of its origin are gone", use an idiomatic cast.
next prev parent reply other threads:[~2019-03-29 19:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-29 16:30 [PATCH v2 1/4] kernel.h: use parentheses around argument in u64_to_user_ptr() Jann Horn
2019-03-29 16:30 ` [PATCH v2 2/4] x86/microcode: Fix __user annotations around generic_load_microcode() Jann Horn
2019-03-29 16:30 ` [PATCH v2 3/4] x86/fpu: Fix __user annotations Jann Horn
2019-03-29 18:03 ` Luc Van Oostenryck
2019-03-29 19:25 ` Jann Horn
2019-03-29 19:42 ` Al Viro [this message]
2019-03-29 16:30 ` [PATCH v2 4/4] x86/uaccess: Fix implicit cast of __user pointer Jann Horn
2019-03-29 20:27 ` Mukesh Ojha
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