From: Andy Lutomirski <luto@kernel.org> To: x86@kernel.org Cc: Borislav Petkov <bp@alien8.de>, linux-kernel@vger.kernel.org, Brian Gerst <brgerst@gmail.com>, Jann Horn <jann@thejh.net>, Josh Poimboeuf <jpoimboe@redhat.com>, Andy Lutomirski <luto@kernel.org> Subject: [PATCH v2 2/8] sched: Add try_get_task_stack() and put_task_stack() Date: Thu, 15 Sep 2016 22:45:43 -0700 Message-ID: <17a434f50ad3d77000104f21666575e10a9c1fbd.1474003868.git.luto@kernel.org> (raw) In-Reply-To: <cover.1474003868.git.luto@kernel.org> In-Reply-To: <cover.1474003868.git.luto@kernel.org> There are a few places in the kernel that access stack memory belonging to a different task. Before we can start freeing task stacks before the task_struct is freed, we need a way for those code paths to pin the stack. Signed-off-by: Andy Lutomirski <luto@kernel.org> --- include/linux/sched.h | 16 ++++++++++++++++ init/Kconfig | 3 +++ 2 files changed, 19 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index a287e8b13549..a95867267e9f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -3094,11 +3094,19 @@ static inline struct thread_info *task_thread_info(struct task_struct *task) { return &task->thread_info; } + +/* + * When accessing the stack of a non-current task that might exit, use + * try_get_task_stack() instead. task_stack_page will return a pointer + * that could get freed out from under you. + */ static inline void *task_stack_page(const struct task_struct *task) { return task->stack; } + #define setup_thread_stack(new,old) do { } while(0) + static inline unsigned long *end_of_stack(const struct task_struct *task) { return task->stack; @@ -3134,6 +3142,14 @@ static inline unsigned long *end_of_stack(struct task_struct *p) } #endif + +static inline void *try_get_task_stack(struct task_struct *tsk) +{ + return task_stack_page(tsk); +} + +static inline void put_task_stack(struct task_struct *tsk) {} + #define task_stack_end_corrupted(task) \ (*(end_of_stack(task)) != STACK_END_MAGIC) diff --git a/init/Kconfig b/init/Kconfig index ec8d43894b02..3b9a47fe843b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -33,6 +33,9 @@ config THREAD_INFO_IN_TASK make this work, an arch will need to remove all thread_info fields except flags and fix any runtime bugs. + One subtle change that will be needed is to use try_get_task_stack() + and put_task_stack() in save_thread_stack_tsk() and get_wchan(). + menu "General setup" config BROKEN -- 2.7.4
next prev parent reply index Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-16 5:45 [PATCH v2 0/8] thread_info cleanups and stack caching Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 1/8] x86/entry/64: Fix a minor comment rebase error Andy Lutomirski 2016-09-16 9:16 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` Andy Lutomirski [this message] 2016-09-16 9:16 ` [tip:x86/asm] sched/core: Add try_get_task_stack() and put_task_stack() tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 3/8] kthread: to_live_kthread() needs try_get_task_stack() Andy Lutomirski 2016-09-16 9:17 ` [tip:x86/asm] kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function tip-bot for Oleg Nesterov 2016-09-16 5:45 ` [PATCH v2 4/8] x86/dumpstack: Pin the target stack when dumping it Andy Lutomirski 2016-09-16 9:17 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 11:55 ` Josh Poimboeuf 2016-09-16 12:28 ` Josh Poimboeuf 2016-09-16 12:57 ` Ingo Molnar 2016-09-16 13:05 ` [PATCH] x86/dumpstack: remove NULL task pointer convention Josh Poimboeuf 2016-09-16 5:45 ` [PATCH v2 5/8] x86/process: Pin the target stack in get_wchan() Andy Lutomirski 2016-09-16 9:18 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 6/8] lib/syscall: Pin the task stack in collect_syscall() Andy Lutomirski 2016-09-16 9:18 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 7/8] sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK Andy Lutomirski 2016-09-16 9:19 ` [tip:x86/asm] sched/core: " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 8/8] fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set Andy Lutomirski 2016-09-16 9:19 ` [tip:x86/asm] fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y tip-bot for Andy Lutomirski
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=17a434f50ad3d77000104f21666575e10a9c1fbd.1474003868.git.luto@kernel.org \ --to=luto@kernel.org \ --cc=bp@alien8.de \ --cc=brgerst@gmail.com \ --cc=jann@thejh.net \ --cc=jpoimboe@redhat.com \ --cc=linux-kernel@vger.kernel.org \ --cc=x86@kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
LKML Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \ linux-kernel@vger.kernel.org public-inbox-index lkml Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel AGPL code for this site: git clone https://public-inbox.org/public-inbox.git