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Old 03-01-2012, 01:45 PM
Andy Whitcroft
 
Default block: Fix io_context leak after failure of clone with CLONE_IO

From: Louis Rilling <louis.rilling@kerlabs.com>

With CLONE_IO, parent's io_context->nr_tasks is incremented, but never
decremented whenever copy_process() fails afterwards, which prevents
exit_io_context() from calling IO schedulers exit functions.

Give a task_struct to exit_io_context(), and call exit_io_context() instead of
put_io_context() in copy_process() cleanup path.

Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

(cherry picked from commit b69f2292063d2caf37ca9aec7d63ded203701bf3)
CVE-2012-0879
BugLink: http://bugs.launchpad.net/bugs/940743
Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
block/blk-ioc.c | 10 +++++-----
include/linux/iocontext.h | 5 +++--
kernel/exit.c | 2 +-
kernel/fork.c | 3 ++-
4 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index dcd0412..cbdabb0 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -66,14 +66,14 @@ static void cfq_exit(struct io_context *ioc)
}

/* Called by the exitting task */
-void exit_io_context(void)
+void exit_io_context(struct task_struct *task)
{
struct io_context *ioc;

- task_lock(current);
- ioc = current->io_context;
- current->io_context = NULL;
- task_unlock(current);
+ task_lock(task);
+ ioc = task->io_context;
+ task->io_context = NULL;
+ task_unlock(task);

if (atomic_dec_and_test(&ioc->nr_tasks)) {
if (ioc->aic && ioc->aic->exit)
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index eb73632..19abfc1 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -94,14 +94,15 @@ static inline struct io_context *ioc_task_link(struct io_context *ioc)
return NULL;
}

+struct task_struct;
#ifdef CONFIG_BLOCK
int put_io_context(struct io_context *ioc);
-void exit_io_context(void);
+void exit_io_context(struct task_struct *task);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
void copy_io_context(struct io_context **pdst, struct io_context **psrc);
#else
-static inline void exit_io_context(void)
+static inline void exit_io_context(struct task_struct *task)
{
}

diff --git a/kernel/exit.c b/kernel/exit.c
index 0f8fae3..a2a1659 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1020,7 +1020,7 @@ NORET_TYPE void do_exit(long code)
tsk->flags |= PF_EXITPIDONE;

if (tsk->io_context)
- exit_io_context();
+ exit_io_context(tsk);

if (tsk->splice_pipe)
__free_pipe_info(tsk->splice_pipe);
diff --git a/kernel/fork.c b/kernel/fork.c
index 4bde56f..cd075bc 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1299,7 +1299,8 @@ bad_fork_free_pid:
if (pid != &init_struct_pid)
free_pid(pid);
bad_fork_cleanup_io:
- put_io_context(p->io_context);
+ if (p->io_context)
+ exit_io_context(p);
bad_fork_cleanup_namespaces:
exit_task_namespaces(p);
bad_fork_cleanup_mm:
--
1.7.9


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