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authorPeilin Ye <yepeilin.cs@gmail.com>2020-09-24 16:43:48 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2020-09-25 11:29:22 +0300
commit5af08640795b2b9a940c9266c0260455377ae262 (patch)
tree5a91488b8c1ddd580e40f4cc56b725a72e68e537 /drivers/video
parent6735b4632def0640dbdf4eb9f99816aca18c4f16 (diff)
downloadlinux-5af08640795b2b9a940c9266c0260455377ae262.tar.xz
fbcon: Fix global-out-of-bounds read in fbcon_get_font()
fbcon_get_font() is reading out-of-bounds. A malicious user may resize `vc->vc_font.height` to a large value, causing fbcon_get_font() to read out of `fontdata`. fbcon_get_font() handles both built-in and user-provided fonts. Fortunately, recently we have added FONT_EXTRA_WORDS support for built-in fonts, so fix it by adding range checks using FNTSIZE(). This patch depends on patch "fbdev, newport_con: Move FONT_EXTRA_WORDS macros into linux/font.h", and patch "Fonts: Support FONT_EXTRA_WORDS macros for built-in fonts". Cc: stable@vger.kernel.org Reported-and-tested-by: syzbot+29d4ed7f3bdedf2aa2fd@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=08b8be45afea11888776f897895aef9ad1c3ecfd Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/b34544687a1a09d6de630659eb7a773f4953238b.1600953813.git.yepeilin.cs@gmail.com
Diffstat (limited to 'drivers/video')
-rw-r--r--drivers/video/fbdev/core/fbcon.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 8a31fc2b2258..e432c9f09c13 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2471,6 +2471,9 @@ static int fbcon_get_font(struct vc_data *vc, struct console_font *font)
if (font->width <= 8) {
j = vc->vc_font.height;
+ if (font->charcount * j > FNTSIZE(fontdata))
+ return -EINVAL;
+
for (i = 0; i < font->charcount; i++) {
memcpy(data, fontdata, j);
memset(data + j, 0, 32 - j);
@@ -2479,6 +2482,9 @@ static int fbcon_get_font(struct vc_data *vc, struct console_font *font)
}
} else if (font->width <= 16) {
j = vc->vc_font.height * 2;
+ if (font->charcount * j > FNTSIZE(fontdata))
+ return -EINVAL;
+
for (i = 0; i < font->charcount; i++) {
memcpy(data, fontdata, j);
memset(data + j, 0, 64 - j);
@@ -2486,6 +2492,9 @@ static int fbcon_get_font(struct vc_data *vc, struct console_font *font)
fontdata += j;
}
} else if (font->width <= 24) {
+ if (font->charcount * (vc->vc_font.height * sizeof(u32)) > FNTSIZE(fontdata))
+ return -EINVAL;
+
for (i = 0; i < font->charcount; i++) {
for (j = 0; j < vc->vc_font.height; j++) {
*data++ = fontdata[0];
@@ -2498,6 +2507,9 @@ static int fbcon_get_font(struct vc_data *vc, struct console_font *font)
}
} else {
j = vc->vc_font.height * 4;
+ if (font->charcount * j > FNTSIZE(fontdata))
+ return -EINVAL;
+
for (i = 0; i < font->charcount; i++) {
memcpy(data, fontdata, j);
memset(data + j, 0, 128 - j);