linux-kernel - [PATCH 4.9 037/128] video: fbdev: w100fb: Fix a potential double free.

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Date:   Fri, 19 Jun 2020 16:32:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Richard Purdie <rpurdie@...ys.net>,
        Antonino Daplas <adaplas@....net>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Sam Ravnborg <sam@...nborg.org>
Subject: [PATCH 4.9 037/128] video: fbdev: w100fb: Fix a potential double free.

From: Christophe JAILLET <christophe.jaillet@...adoo.fr>

commit 18722d48a6bb9c2e8d046214c0a5fd19d0a7c9f6 upstream.

Some memory is vmalloc'ed in the 'w100fb_save_vidmem' function and freed in
the 'w100fb_restore_vidmem' function. (these functions are called
respectively from the 'suspend' and the 'resume' functions)

However, it is also freed in the 'remove' function.

In order to avoid a potential double free, set the corresponding pointer
to NULL once freed in the 'w100fb_restore_vidmem' function.

Fixes: aac51f09d96a ("[PATCH] w100fb: Rewrite for platform independence")
Cc: Richard Purdie <rpurdie@...ys.net>
Cc: Antonino Daplas <adaplas@....net>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc: <stable@...r.kernel.org> # v2.6.14+
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Signed-off-by: Sam Ravnborg <sam@...nborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200506181902.193290-1-christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/video/fbdev/w100fb.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/video/fbdev/w100fb.c
+++ b/drivers/video/fbdev/w100fb.c
@@ -583,6 +583,7 @@ static void w100fb_restore_vidmem(struct
 		memsize=par->mach->mem->size;
 		memcpy_toio(remapped_fbuf + (W100_FB_BASE-MEM_WINDOW_BASE), par->saved_extmem, memsize);
 		vfree(par->saved_extmem);
+		par->saved_extmem = NULL;
 	}
 	if (par->saved_intmem) {
 		memsize=MEM_INT_SIZE;
@@ -591,6 +592,7 @@ static void w100fb_restore_vidmem(struct
 		else
 			memcpy_toio(remapped_fbuf + (W100_FB_BASE-MEM_WINDOW_BASE), par->saved_intmem, memsize);
 		vfree(par->saved_intmem);
+		par->saved_intmem = NULL;
 	}
 }