From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2C7958F5E; Tue, 8 Jul 2025 16:59:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751993950; cv=none; b=q2syV503pO/IJ9xPaQo8S09P2nYSrNv0b2nWo4Jo6WxTI6rGLRCC9OGQcCL8T9WQB4J1wPPupE3UtHmm4iitU8/4S+2MMFDRfbM1YQsHhnnXgZmyILDUs5YCYj6viDr6AuOr1IFEwbStrD4y/wNzPbqdUTAgTnB1zicWfWiJbDQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751993950; c=relaxed/simple; bh=WlqP1P6gRj9MTyBkOWxqgd7b2CVTcxy1jeg3Q34VnCw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=T4BcB2QYvh/qiVS44O1zOdCsTzYLphHpcnq1IpoxwgMhg95wfWJEodgiPow3naK7EAVz5SRfbSPWGYlFqOLIcPK1ctssgQXU5eedQ0pVaYloT3AnQ5fDFbGw0MJ339IXlibYsDAjCNtkU7LboZsIKcyPlTQSUAVijDFSy1l81sM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1gJa3YG3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1gJa3YG3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5792FC4CEED; Tue, 8 Jul 2025 16:59:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751993949; bh=WlqP1P6gRj9MTyBkOWxqgd7b2CVTcxy1jeg3Q34VnCw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1gJa3YG3Wy21zrMPTLZ1Cuu/vH8LPgX5/xYXOXIYERwiQPSDStyoImcWzMx62X88d ydhF52psbVW8Mb+BzQMVYT3HmOF9+YrmKWaNQKCOu0vAksqb8rmpNeFW3+b5eEcSLX jOKt5n+jaqXD6sqGl01wHTSXnq1rZ6LN8rFlzJmc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Murad Masimov , Helge Deller , Sasha Levin Subject: [PATCH 5.15 044/160] fbdev: Fix do_register_framebuffer to prevent null-ptr-deref in fb_videomode_to_var Date: Tue, 8 Jul 2025 18:21:21 +0200 Message-ID: <20250708162232.760659324@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250708162231.503362020@linuxfoundation.org> References: <20250708162231.503362020@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Murad Masimov [ Upstream commit 17186f1f90d34fa701e4f14e6818305151637b9e ] If fb_add_videomode() in do_register_framebuffer() fails to allocate memory for fb_videomode, it will later lead to a null-ptr dereference in fb_videomode_to_var(), as the fb_info is registered while not having the mode in modelist that is expected to be there, i.e. the one that is described in fb_info->var. ================================================================ general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 1 PID: 30371 Comm: syz-executor.1 Not tainted 5.10.226-syzkaller #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:fb_videomode_to_var+0x24/0x610 drivers/video/fbdev/core/modedb.c:901 Call Trace: display_to_var+0x3a/0x7c0 drivers/video/fbdev/core/fbcon.c:929 fbcon_resize+0x3e2/0x8f0 drivers/video/fbdev/core/fbcon.c:2071 resize_screen drivers/tty/vt/vt.c:1176 [inline] vc_do_resize+0x53a/0x1170 drivers/tty/vt/vt.c:1263 fbcon_modechanged+0x3ac/0x6e0 drivers/video/fbdev/core/fbcon.c:2720 fbcon_update_vcs+0x43/0x60 drivers/video/fbdev/core/fbcon.c:2776 do_fb_ioctl+0x6d2/0x740 drivers/video/fbdev/core/fbmem.c:1128 fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1203 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:739 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x67/0xd1 ================================================================ Even though fbcon_init() checks beforehand if fb_match_mode() in var_to_display() fails, it can not prevent the panic because fbcon_init() does not return error code. Considering this and the comment in the code about fb_match_mode() returning NULL - "This should not happen" - it is better to prevent registering the fb_info if its mode was not set successfully. Also move fb_add_videomode() closer to the beginning of do_register_framebuffer() to avoid having to do the cleanup on fail. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Murad Masimov Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/core/fbmem.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 5e8ee360f6ba2..a8d6bd465ffe4 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1622,7 +1622,7 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, static int do_register_framebuffer(struct fb_info *fb_info) { - int i; + int i, err = 0; struct fb_videomode mode; if (fb_check_foreignness(fb_info)) @@ -1635,10 +1635,18 @@ static int do_register_framebuffer(struct fb_info *fb_info) if (num_registered_fb == FB_MAX) return -ENXIO; - num_registered_fb++; for (i = 0 ; i < FB_MAX; i++) if (!registered_fb[i]) break; + + if (!fb_info->modelist.prev || !fb_info->modelist.next) + INIT_LIST_HEAD(&fb_info->modelist); + + fb_var_to_videomode(&mode, &fb_info->var); + err = fb_add_videomode(&mode, &fb_info->modelist); + if (err < 0) + return err; + fb_info->node = i; refcount_set(&fb_info->count, 1); mutex_init(&fb_info->lock); @@ -1671,16 +1679,12 @@ static int do_register_framebuffer(struct fb_info *fb_info) if (!fb_info->pixmap.blit_y) fb_info->pixmap.blit_y = ~(u32)0; - if (!fb_info->modelist.prev || !fb_info->modelist.next) - INIT_LIST_HEAD(&fb_info->modelist); - if (fb_info->skip_vt_switch) pm_vt_switch_required(fb_info->dev, false); else pm_vt_switch_required(fb_info->dev, true); - fb_var_to_videomode(&mode, &fb_info->var); - fb_add_videomode(&mode, &fb_info->modelist); + num_registered_fb++; registered_fb[i] = fb_info; #ifdef CONFIG_GUMSTIX_AM200EPD -- 2.39.5