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Fri, 21 Jul 2023 12:58:37 +0200 (CEST) Message-ID: <20230721105743.954526690@infradead.org> User-Agent: quilt/0.66 Date: Fri, 21 Jul 2023 12:22:41 +0200 From: Peter Zijlstra To: tglx@linutronix.de, axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net, andrealmeid@igalia.com, Andrew Morton , urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com, Arnd Bergmann , linux-api@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, malteskarupke@web.de Subject: [PATCH v1 04/14] futex: Validate futex value against futex size References: <20230721102237.268073801@infradead.org> MIME-Version: 1.0 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 20D8B40011 X-Stat-Signature: gft7a6kgf1trs3obz1qwzjnbs4zz89by X-Rspam-User: X-HE-Tag: 1689937129-217362 X-HE-Meta: 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 CvVu7MCo 7Ly2UGncuyzBMqDv3IX0+Q5unct0hsqL893CsEMaTJKervlyreSd+ArSNGXS9b/H67opu1NEJiFyRlAYNrAecuYZO3w89FS7F6IICVXanXpYNDUzito+4CaxW3B/5HAp4PI+Ffhr5D7SDA9ybuXMYqJr2AGMBG6D0jYZPFlXFD7grUJ5qqgo9X0BbVvJr4ATifjpmncYG7WOr8zGYZxx0UWa1/W+9vaE2kjhmBI66LYPstsKO8IW0JX+zotqybTQYMegJwwgl6ug4VN7FJ3nZRIHdNQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Ensure the futex value fits in the given futex size. Since this adds a constraint to an existing syscall, it might possibly change behaviour. Currently the value would be truncated to a u32 and any high bits would get silently lost. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner --- kernel/futex/futex.h | 8 ++++++++ kernel/futex/syscalls.c | 3 +++ 2 files changed, 11 insertions(+) --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -86,6 +86,14 @@ static inline unsigned int futex_size(un return 1 << size; /* {0,1,2,3} -> {1,2,4,8} */ } +static inline bool futex_validate_input(unsigned int flags, u64 val) +{ + int bits = 8 * futex_size(flags); + if (bits < 64 && (val >> bits)) + return false; + return true; +} + #ifdef CONFIG_FAIL_FUTEX extern bool should_fail_futex(bool fshared); #else --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -209,6 +209,9 @@ static int futex_parse_waitv(struct fute if (!futex_flags_valid(flags)) return -EINVAL; + if (!futex_validate_input(flags, aux.val)) + return -EINVAL; + futexv[i].w.flags = flags; futexv[i].w.val = aux.val; futexv[i].w.uaddr = aux.uaddr;