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Mon, 02 Nov 2026 19:44:42 -0800 (PST) Received: from osman.mioffice.cn ([43.224.245.178]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b07c7dea24sm1820235a91.5.2026.11.02.19.44.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 19:44:42 -0800 (PST) From: Zhan Xusheng To: tglx@kernel.org Cc: thomas.weissschuh@linutronix.de, yury.norov@gmail.com, linux@rasmusvillemoes.dk, luto@kernel.org, vincenzo.frascino@arm.com, david.laight.linux@gmail.com, linux-kernel@vger.kernel.org, zhanxusheng@xiaomi.com Subject: [PATCH RESEND] vdso/gettimeofday: Assert that the clockid fits into the u32 bitmask Date: Tue, 3 Nov 2026 11:44:36 +0800 Message-ID: <20261103034436.1521751-1-zhanxusheng1024@gmail.com> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Zhan Xusheng __cvdso_clock_gettime_common() and __cvdso_clock_getres_common() turn the clockid into a bitmask: msk = 1U << clock; The shift count stays in range because vdso_clockid_valid() rejects anything above CLOCK_AUX_LAST, which is 23. Nothing records that, so raising MAX_AUX_CLOCKS past 16 would take CLOCK_AUX_LAST to 32 and make the shift undefined. Assert it in vdso_clockid_valid(), which is where the bound comes from and covers both conversion sites. 8 * sizeof(u32) rather than BITS_PER_TYPE(): the latter lives in linux/bits.h, which lib/vdso/gettimeofday.c only reaches on architectures whose asm/vdso/gettimeofday.h happens to pull it in. MAX_AUX_CLOCKS=16 still builds, 17 trips the assert. Suggested-by: Thomas Gleixner Signed-off-by: Zhan Xusheng --- Resending since 7.4-rc1 is out. This replaces v7 5/5 of https://lore.kernel.org/all/20261002153104.1347978-1-zhanxusheng@xiaomi.com/ 1-3 of that series are in 7.4-rc1; 4/5 is no longer needed. It now asserts on CLOCK_AUX_LAST in vdso_clockid_valid(), as suggested. lib/vdso/gettimeofday.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index a324b2f2ec6c..67c9bcdd9aeb 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -99,6 +99,12 @@ static __always_inline const struct vdso_time_data *__arch_get_vdso_u_time_data( static __always_inline bool vdso_clockid_valid(clockid_t clock) { + /* + * The callers turn an accepted clockid into a bitmask with + * 1U << clock, so the largest one has to fit into that u32. + */ + BUILD_BUG_ON(CLOCK_AUX_LAST >= 8 * sizeof(u32)); + /* Check for negative values or invalid clocks */ return likely((u32) clock <= CLOCK_AUX_LAST); } -- 2.43.0