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[59.125.13.244]) by smtp.gmail.com with ESMTPSA id z21sm688157pfa.158.2020.10.31.00.28.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Oct 2020 00:28:20 -0700 (PDT) From: Peilin Ye To: Daniel Vetter , Greg Kroah-Hartman , Jiri Slaby , Thomas Winischhofer Cc: Bartlomiej Zolnierkiewicz , Nicolas Pitre , "Gustavo A . R . Silva" , Tetsuo Handa , George Kennedy , Nathan Chancellor , Peter Rosin , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, Peilin Ye Subject: [PATCH 2/2] fbcon: Prevent global-out-of-bounds read in fbcon_copy_font() Date: Sat, 31 Oct 2020 03:27:23 -0400 Message-Id: <64b792b83119b0ec6caed9cb62087453b675c690.1604128640.git.yepeilin.cs@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org fbcon_copy_font() is using a signed int, `con`, as an index into `fb_display[MAX_NR_CONSOLES]`, without bounds checking. In con_font_copy(), `con` is being silently casted from the unsigned `op->height`. Let con_font_copy() and fbcon_copy_font() pass `op->height` directly, and add a range check in fbcon_copy_font(). Also, add a comment in con_font_op() for less confusion, since ideally `op->height` should not be used as a console index, as the field name suggests. This patch depends on patch "console: Remove dummy con_font_op callback implementations". Cc: stable@vger.kernel.org Signed-off-by: Peilin Ye --- drivers/tty/vt/vt.c | 6 +++--- drivers/video/fbdev/core/fbcon.c | 8 ++++++-- include/linux/console.h | 2 +- 3 files changed, 10 insertions(+), 6 deletions(-) diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 9506a76f3ab6..ff8ea1654a69 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -4704,9 +4704,8 @@ static int con_font_default(struct vc_data *vc, struct console_font_op *op) return rc; } -static int con_font_copy(struct vc_data *vc, struct console_font_op *op) +static int con_font_copy(struct vc_data *vc, unsigned int con) { - int con = op->height; int rc; @@ -4735,7 +4734,8 @@ int con_font_op(struct vc_data *vc, struct console_font_op *op) case KD_FONT_OP_SET_DEFAULT: return con_font_default(vc, op); case KD_FONT_OP_COPY: - return con_font_copy(vc, op); + /* uses op->height as a console index */ + return con_font_copy(vc, op->height); } return -ENOSYS; } diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index cef437817b0d..1caa98146712 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2451,11 +2451,15 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, return 0; } -static int fbcon_copy_font(struct vc_data *vc, int con) +static int fbcon_copy_font(struct vc_data *vc, unsigned int con) { - struct fbcon_display *od = &fb_display[con]; + struct fbcon_display *od; struct console_font *f = &vc->vc_font; + if (con >= MAX_NR_CONSOLES) + return -EINVAL; + + od = &fb_display[con]; if (od->fontdata == f->data) return 0; /* already the same font... */ return fbcon_do_set_font(vc, f->width, f->height, od->fontdata, od->userfont); diff --git a/include/linux/console.h b/include/linux/console.h index 4b1e26c4cb42..34855d3f2afd 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -62,7 +62,7 @@ struct consw { int (*con_font_get)(struct vc_data *vc, struct console_font *font); int (*con_font_default)(struct vc_data *vc, struct console_font *font, char *name); - int (*con_font_copy)(struct vc_data *vc, int con); + int (*con_font_copy)(struct vc_data *vc, unsigned int con); int (*con_resize)(struct vc_data *vc, unsigned int width, unsigned int height, unsigned int user); void (*con_set_palette)(struct vc_data *vc, -- 2.25.1