linux-kernel - [PATCH v2] fork: fix oops after fork failure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 23 Aug 2012 19:36:08 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	<linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	<torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Glauber Costa <glommer@...allels.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH v2] fork: fix oops after fork failure

When we want to duplicate a new process, dup_task_struct() will undergo
a series of allocations. If alloc_thread_info_node() fails, we call
free_task_struct() and return.

This seems right, but it is not. free_task_struct() will not only free
the task struct from the kmem_cache, but will also call
arch_release_task_struct(). The problem is that this function is
supposed to undo whatever arch-specific work done by
arch_dup_task_struct(), that is not yet called at this point.  The
particular problem I ran accross was that in x86, we will arrive at
fpu_free() without having ever allocated it.

Signed-off-by: Glauber Costa <glommer@...allels.com>
Reported-by: Frederic Weisbecker <fweisbec@...hat.com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Tony Luck <tony.luck@...el.com>
CC: Fenghua Yu <fenghua.yu@...el.com>
---
 arch/ia64/include/asm/thread_info.h | 2 +-
 kernel/fork.c                       | 9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/ia64/include/asm/thread_info.h b/arch/ia64/include/asm/thread_info.h
index f7ee853..62452bd 100644
--- a/arch/ia64/include/asm/thread_info.h
+++ b/arch/ia64/include/asm/thread_info.h
@@ -90,7 +90,7 @@ struct thread_info {
 										\
 	ret;									\
 })
-#define free_task_struct(tsk)	free_pages((unsigned long) (tsk), KERNEL_STACK_SIZE_ORDER)
+#define __free_task_struct(tsk)	free_pages((unsigned long) (tsk), KERNEL_STACK_SIZE_ORDER)
 
 #endif /* !__ASSEMBLY */
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 152d023..76acb1a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -124,10 +124,15 @@ static inline struct task_struct *alloc_task_struct_node(int node)
 
 void __weak arch_release_task_struct(struct task_struct *tsk) { }
 
+static inline void __free_task_struct(struct task_struct *tsk)
+{
+	kmem_cache_free(task_struct_cachep, tsk);
+}
+
 static inline void free_task_struct(struct task_struct *tsk)
 {
 	arch_release_task_struct(tsk);
-	kmem_cache_free(task_struct_cachep, tsk);
+	__free_task_struct(tsk);
 }
 #endif
 
@@ -299,7 +304,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 
 	ti = alloc_thread_info_node(tsk, node);
 	if (!ti) {
-		free_task_struct(tsk);
+		__free_task_struct(tsk);
 		return NULL;
 	}
 
-- 
1.7.11.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/