linux-kernel - [PATCH 1/2] ps3fb: prevent use after free of fb

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Date:	Fri, 11 Jan 2008 14:27:10 +0100 (CET)
From:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
cc:	Jeremy Kerr <jk@...abs.org>,
	Cell Broadband Engine OSS Development 
	<cbe-oss-dev@...abs.org>,
	Linux/PPC Development <linuxppc-dev@...abs.org>,
	Linux Frame Buffer Device Development 
	<linux-fbdev-devel@...ts.sourceforge.net>
Subject: [PATCH 1/2] ps3fb: prevent use after free of fb_info

From: Jeremy Kerr <jk@...abs.org>

In ps3fb_shutdown, freeing the framebuffer will cause fb_info (in
dev->core.driver_data) to be free()ed, which we potentially access
from the ps3fbd kthread.

This change frees the framebuffer after stopping the ps3fbd kthread.

Signed-off-by: Jeremy Kerr <jk@...abs.org>
Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
---
 drivers/video/ps3fb.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/video/ps3fb.c
+++ b/drivers/video/ps3fb.c
@@ -1234,12 +1234,6 @@ static int ps3fb_shutdown(struct ps3_sys
 	ps3fb_flip_ctl(0, &ps3fb);	/* flip off */
 	ps3fb.dinfo->irq.mask = 0;
 
-	if (info) {
-		unregister_framebuffer(info);
-		fb_dealloc_cmap(&info->cmap);
-		framebuffer_release(info);
-	}
-
 	ps3av_register_flip_ctl(NULL, NULL);
 	if (ps3fb.task) {
 		struct task_struct *task = ps3fb.task;
@@ -1250,6 +1244,12 @@ static int ps3fb_shutdown(struct ps3_sys
 		free_irq(ps3fb.irq_no, &dev->core);
 		ps3_irq_plug_destroy(ps3fb.irq_no);
 	}
+	if (info) {
+		unregister_framebuffer(info);
+		fb_dealloc_cmap(&info->cmap);
+		framebuffer_release(info);
+		info = dev->core.driver_data = NULL;
+	}
 	iounmap((u8 __iomem *)ps3fb.dinfo);
 
 	status = lv1_gpu_context_free(ps3fb.context_handle);

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Network and Software Technology Center Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone:    +32 (0)2 700 8453
Fax:      +32 (0)2 700 8622
E-mail:   Geert.Uytterhoeven@...ycom.com
Internet: http://www.sony-europe.com/

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