From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793831457; b=ai6VNeeOkUp36LGpO70/u/z8IIic+EIJgIE/Q2qYzM72crY8EW9YYq2ZN2exbayaDHF8 oOfnc9/9uAiJDHxRpO8ZmFI4cYMa9625pr0b+6noluHjq3jAyEY19g6oxlyRg+dtG0bzB OMMPMS2zVf7/R0aZyZkp+jmpiU+Wib6DC9ECSvwuslp2x/1Hr6KxUUL/tJJqonBBWKAud u5oqT2p3s1nnnwRfw+Z1pJ/5kiwG1/1kJp/baChlIPbbmoz1o80LEl68PGp2ChbEMA4vk u4wjKKKS/t7rfaVreT6Knx6PS2LFQyHxwtCP33Tvx1aJNyqaFyex27zEWLXmfBRwXXg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831457; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=XneJ46nusQ+0fmVlY8i6RjFTkcBAV3duvaJ2UrGqAQo=; b=xdMJCA+6KOQ6Xn0JN1EXHmIMngrju+Qyv1ycSA6mPZzq1o79y+jxgAINvCcbfjZABVbP DGrfIxchGyGsKHoX23e46X6UORaLFzGW6I6Fod7YLqh0CZI/EpoXHs9TpDyTUch43WkAw sAqVGld3TRnpj9M5F8vwoNpXmU/xeDEhbhuAOAk3J2upatW9Pvs7mJEwiivyhsWq/m4zN js6B3g7JbfC4Ektx6V+CxMBvoCGTPQw8nw/PPmxuI9lh0A/I8vfSgihe5dFeSYF1zznk0 6X1RLT+gR0ekEeFXdPZp48C1g3ILbBLOy9yi4Q+3B/QqJZy+O+NWkR3VZVv00rVV12g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=Zz8I6Q1B; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3190E606A335; Wed, 4 Nov 2026 22:30:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=Zz8I6Q1B Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB5F81F000C1; Wed, 4 Nov 2026 22:30:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831457; bh=XneJ46nusQ+0fmVlY8i6RjFTkcBAV3duvaJ2UrGqAQo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Zz8I6Q1BUTpKLQymk/XV9Fpf6W6+NvvEy62Mp/swAbK0KFMW0stkV7de/NbGZZKfl QQ9/XH4V1dPw0z95SqV+PvcDNrISYvUuE033/XGjMP6pHvUMLv6yJX7Yd0aabcWT+r 9ebiO4rPEnmByhz/1aC/sDn3SeDcgSKYCVWYxPqg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, co+ed9902f2e44184d9@bugs.sh, Xiang Mei , Helge Deller Subject: [PATCH 6.18 0712/1005] fbdev: udlfb: dont rebuild the mode list while the framebuffer is in use Date: Wed, 4 Nov 2026 16:07:25 -0500 Message-ID: <20261104211103.499074912@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiang Mei commit ac9cfa552102b8e80e88c2872e80dc9cb5f07dda upstream. dlfb_setup_modes() frees info->modelist with fb_destroy_modelist() and rebuilds it, but fbcon holds raw pointers into that list in fb_display[i].mode and nothing un-publishes them the way do_unregister_framebuffer() and store_modes() do with fbcon_delete_modelist(). The function does refuse to install a new mode while the framebuffer has users (dlfb->fb_count != 0), but only after the list is already destroyed. Reached from the 0666 "edid" sysfs attribute, an unprivileged write to /sys/class/graphics/fb0/edid therefore fails with -EINVAL and still leaves every fb_display[i].mode dangling; the next console switch reads the freed fb_videomode in fb_videomode_to_var(). Test fb_count before touching the list. fbcon takes a reference through fbcon_open(), so that condition covers exactly the states in which fb_display[] points into the list, and the errno returned to userspace is unchanged. BUG: KASAN: slab-use-after-free in fb_videomode_to_var (drivers/video/fbdev/core/modedb.c:905) Read of size 4 at addr ffff8880107b449c by task kworker/1:1/47 Workqueue: events console_callback Call Trace: fb_videomode_to_var (drivers/video/fbdev/core/modedb.c:905) display_to_var (drivers/video/fbdev/core/fbcon.c:998) fbcon_switch (drivers/video/fbdev/core/fbcon.c:2182) redraw_screen (drivers/tty/vt/vt.c:994) complete_change_console (drivers/tty/vt/vt_ioctl.c:1141) console_callback (drivers/tty/vt/vt.c:3358) process_one_work (kernel/workqueue.c:3396) worker_thread (kernel/workqueue.c:3479 kernel/workqueue.c:3560) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245) ... The buggy address is located 28 bytes inside of freed 96-byte region [ffff8880107b4480, ffff8880107b44e0) Cc: stable@vger.kernel.org Fixes: 7d9485e2c53c ("Staging: udlfb: Add functions to expose sysfs metrics and controls") Reported-by: co+ed9902f2e44184d9@bugs.sh Closes: https://lore.kernel.org/all/1jSCSNaDKmuUG7h40rTsSl1rMaSwdlJef4rp%40bugs.sh/ Assisted-by: Claude:claude-opus-5 Signed-off-by: Xiang Mei Link: https://lore.kernel.org/all/1jSCSNaDKmuUG7h40rTsSl1rMaSwdlJef4rp%40bugs.sh/ Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/udlfb.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/video/fbdev/udlfb.c +++ b/drivers/video/fbdev/udlfb.c @@ -1293,6 +1293,11 @@ static int dlfb_setup_modes(struct dlfb_ goto error; } + if (dlfb->fb_count) { + result = -EINVAL; + goto error; + } + fb_destroy_modelist(&info->modelist); memset(&info->monspecs, 0, sizeof(info->monspecs));