From: Andrey Ryabinin <aryabinin@virtuozzo.com> To: <linux-kernel@vger.kernel.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>, Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, Sasha Levin <sasha.levin@oracle.com>, Randy Dunlap <rdunlap@infradead.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Jonathan Corbet <corbet@lwn.net>, Michal Marek <mmarek@suse.cz>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Yury Gribov <y.gribov@samsung.com>, Dmitry Vyukov <dvyukov@google.com>, Konstantin Khlebnikov <koct9i@gmail.com>, Kostya Serebryany <kcc@google.com>, <x86@kernel.org>, <linux-doc@vger.kernel.org>, <linux-kbuild@vger.kernel.org> Subject: [PATCH v4 1/3] kernel: printk: specify alignment for struct printk_log Date: Thu, 3 Dec 2015 18:50:05 +0300 [thread overview] Message-ID: <1449157807-20298-2-git-send-email-aryabinin@virtuozzo.com> (raw) In-Reply-To: <1449157807-20298-1-git-send-email-aryabinin@virtuozzo.com> On architectures that have support for efficient unaligned access struct printk_log has 4-byte alignment. Specify alignment attribute in type declaration. The whole point of this patch is to fix deadlock which happening when UBSAN detects unaligned access in printk() thus UBSAN recursively calls printk() with logbuf_lock held by top printk() call. Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> --- kernel/printk/printk.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 0c9f0250..8712409 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -233,7 +233,11 @@ struct printk_log { u8 facility; /* syslog facility */ u8 flags:5; /* internal record flags */ u8 level:3; /* syslog level */ -}; +} +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS +__packed __aligned(4) +#endif +; /* * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken @@ -274,11 +278,7 @@ static u32 clear_idx; #define LOG_FACILITY(v) ((v) >> 3 & 0xff) /* record buffer */ -#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) -#define LOG_ALIGN 4 -#else #define LOG_ALIGN __alignof__(struct printk_log) -#endif #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); static char *log_buf = __log_buf; -- 2.4.10
WARNING: multiple messages have this Message-ID (diff)
From: Andrey Ryabinin <aryabinin@virtuozzo.com> To: linux-kernel@vger.kernel.org Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>, Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, Sasha Levin <sasha.levin@oracle.com>, Randy Dunlap <rdunlap@infradead.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Jonathan Corbet <corbet@lwn.net>, Michal Marek <mmarek@suse.cz>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Yury Gribov <y.gribov@samsung.com>, Dmitry Vyukov <dvyukov@google.com>, Konstantin Khlebnikov <koct9i@gmail.com>, Kostya Serebryany <kcc@google.com>, x86@kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org Subject: [PATCH v4 1/3] kernel: printk: specify alignment for struct printk_log Date: Thu, 3 Dec 2015 18:50:05 +0300 [thread overview] Message-ID: <1449157807-20298-2-git-send-email-aryabinin@virtuozzo.com> (raw) In-Reply-To: <1449157807-20298-1-git-send-email-aryabinin@virtuozzo.com> On architectures that have support for efficient unaligned access struct printk_log has 4-byte alignment. Specify alignment attribute in type declaration. The whole point of this patch is to fix deadlock which happening when UBSAN detects unaligned access in printk() thus UBSAN recursively calls printk() with logbuf_lock held by top printk() call. Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> --- kernel/printk/printk.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 0c9f0250..8712409 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -233,7 +233,11 @@ struct printk_log { u8 facility; /* syslog facility */ u8 flags:5; /* internal record flags */ u8 level:3; /* syslog level */ -}; +} +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS +__packed __aligned(4) +#endif +; /* * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken @@ -274,11 +278,7 @@ static u32 clear_idx; #define LOG_FACILITY(v) ((v) >> 3 & 0xff) /* record buffer */ -#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) -#define LOG_ALIGN 4 -#else #define LOG_ALIGN __alignof__(struct printk_log) -#endif #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); static char *log_buf = __log_buf; -- 2.4.10
next prev parent reply other threads:[~2015-12-03 15:50 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-12-03 15:50 [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker Andrey Ryabinin 2015-12-03 15:50 ` Andrey Ryabinin 2015-12-03 15:50 ` Andrey Ryabinin [this message] 2015-12-03 15:50 ` [PATCH v4 1/3] kernel: printk: specify alignment for struct printk_log Andrey Ryabinin 2015-12-03 15:50 ` [PATCH v4 2/3] mac80211: Prevent build failure with CONFIG_UBSAN=y Andrey Ryabinin 2015-12-03 15:50 ` Andrey Ryabinin 2015-12-03 17:05 ` Johannes Berg 2015-12-03 19:18 ` Andrey Ryabinin 2015-12-03 15:50 ` [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker Andrey Ryabinin 2015-12-03 15:50 ` Andrey Ryabinin 2015-12-04 14:27 ` kbuild test robot 2015-12-04 14:27 ` kbuild test robot 2015-12-05 0:40 ` Andrew Morton 2015-12-08 23:59 ` Andrew Morton 2015-12-08 23:59 ` Andrew Morton 2015-12-10 1:15 ` Daniel Axtens 2015-12-05 0:37 ` [PATCH v4 0/3] " Andrew Morton 2015-12-05 0:37 ` Andrew Morton 2015-12-07 16:48 ` Andrey Ryabinin 2015-12-07 16:48 ` Andrey Ryabinin 2015-12-10 15:48 ` Andrey Ryabinin 2015-12-10 15:48 ` Andrey Ryabinin
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