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Mon, 19 Jan 2026 07:38:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 12QtJXjfbWm7ZAAAD6G6ig (envelope-from ); Mon, 19 Jan 2026 07:38:32 +0000 Message-ID: <5bc62c51-308c-483f-a92d-29354f2deeac@suse.de> Date: Mon, 19 Jan 2026 08:38:31 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fbdev: sys_fillrect: Add bounds checking to prevent vmalloc-out-of-bounds To: Osama Abdelkader , Zsolt Kajtar , Simona Vetter , Helge Deller , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: syzbot+7a63ce155648954e749b@syzkaller.appspotmail.com References: <20260118001852.70173-1-osama.abdelkader@gmail.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <20260118001852.70173-1-osama.abdelkader@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Score: -2.80 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[gmail.com,c64.rulez.org,ffwll.ch,gmx.de,vger.kernel.org,lists.freedesktop.org]; TAGGED_RCPT(0.00)[7a63ce155648954e749b]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCPT_COUNT_SEVEN(0.00)[8]; FREEMAIL_ENVRCPT(0.00)[gmail.com,gmx.de]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.com:url] X-Spam-Level: X-Spam-Flag: NO Hi, thanks for the patch. Am 18.01.26 um 01:18 schrieb Osama Abdelkader: > The sys_fillrect function was missing bounds validation, which could lead > to vmalloc-out-of-bounds writes when the rectangle coordinates extend > beyond the framebuffer's virtual resolution. This was detected by KASAN > and reported by syzkaller. > > Add validation to: > 1. Check that width and height are non-zero > 2. Verify that dx and dy are within virtual resolution bounds > 3. Clip the rectangle dimensions to fit within virtual resolution if needed This is rather a problem with the caller of the fillrect helper and affects all drivers and all implementations of fb_fillrect. Clipping should happen in the fbcon functions before invoking ->fb_con. Best regards Thomas > > This follows the same pattern used in other framebuffer drivers like > pm2fb_fillrect. > > Reported-by: syzbot+7a63ce155648954e749b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=7a63ce155648954e749b > Signed-off-by: Osama Abdelkader > --- > drivers/video/fbdev/core/sysfillrect.c | 21 ++++++++++++++++++++- > 1 file changed, 20 insertions(+), 1 deletion(-) > > diff --git a/drivers/video/fbdev/core/sysfillrect.c b/drivers/video/fbdev/core/sysfillrect.c > index 12eea3e424bb..73fc322ff8fd 100644 > --- a/drivers/video/fbdev/core/sysfillrect.c > +++ b/drivers/video/fbdev/core/sysfillrect.c > @@ -7,6 +7,7 @@ > #include > #include > #include > +#include > #include > > #ifdef CONFIG_FB_SYS_REV_PIXELS_IN_BYTE > @@ -18,10 +19,28 @@ > > void sys_fillrect(struct fb_info *p, const struct fb_fillrect *rect) > { > + struct fb_fillrect modded; > + int vxres, vyres; > + > if (!(p->flags & FBINFO_VIRTFB)) > fb_warn_once(p, "%s: framebuffer is not in virtual address space.\n", __func__); > > - fb_fillrect(p, rect); > + vxres = p->var.xres_virtual; > + vyres = p->var.yres_virtual; > + > + /* Validate and clip rectangle to virtual resolution */ > + if (!rect->width || !rect->height || > + rect->dx >= vxres || rect->dy >= vyres) > + return; > + > + memcpy(&modded, rect, sizeof(struct fb_fillrect)); > + > + if (modded.dx + modded.width > vxres) > + modded.width = vxres - modded.dx; > + if (modded.dy + modded.height > vyres) > + modded.height = vyres - modded.dy; > + > + fb_fillrect(p, &modded); > } > EXPORT_SYMBOL(sys_fillrect); > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)