[PATCH] CXL: Fix afu_read() not doing finish_wait() on signal or non-blocking

From: Ian Munsie
Date: Wed Oct 08 2014 - 20:19:21 EST


From: Ian Munsie <imunsie@xxxxxxxxxxx>

If afu_read() returned due to a signal or the AFU file descriptor being
opened non-blocking it would not call finish_wait() before returning,
which could lead to a crash later when something else wakes up the wait
queue.

This patch restructures the wait logic to ensure that the cleanup is
done correctly.

Signed-off-by: Ian Munsie <imunsie@xxxxxxxxxxx>
---

Resending with correct whitespace as my mailer decided to replace tabs with
spaces on the last try.

drivers/misc/cxl/file.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 847b7e6..378b099 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -273,6 +273,7 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
struct cxl_context *ctx = file->private_data;
struct cxl_event event;
unsigned long flags;
+ int rc;
DEFINE_WAIT(wait);

if (count < CXL_READ_MIN_SIZE)
@@ -285,13 +286,17 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
if (ctx_event_pending(ctx))
break;

- spin_unlock_irqrestore(&ctx->lock, flags);
- if (file->f_flags & O_NONBLOCK)
- return -EAGAIN;
+ if (file->f_flags & O_NONBLOCK) {
+ rc = -EAGAIN;
+ goto out;
+ }

- if (signal_pending(current))
- return -ERESTARTSYS;
+ if (signal_pending(current)) {
+ rc = -ERESTARTSYS;
+ goto out;
+ }

+ spin_unlock_irqrestore(&ctx->lock, flags);
pr_devel("afu_read going to sleep...\n");
schedule();
pr_devel("afu_read woken up\n");
@@ -336,6 +341,11 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
if (copy_to_user(buf, &event, event.header.size))
return -EFAULT;
return event.header.size;
+
+out:
+ finish_wait(&ctx->wq, &wait);
+ spin_unlock_irqrestore(&ctx->lock, flags);
+ return rc;
}

static const struct file_operations afu_fops = {
--
2.1.0

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