diff options
| author | Samasth Norway Ananda <samasth.norway.ananda@oracle.com> | 2025-09-12 10:00:23 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-10-02 13:44:14 +0200 |
| commit | 4a4bac869560f943edbe3c2b032062f6673b13d3 (patch) | |
| tree | f3273af41e3f6cab194f71bf2cb1dd0a6a3ca21f /drivers | |
| parent | 910d7749346c4b0acdc6e4adfdc4a9984281a206 (diff) | |
| download | linux-4a4bac869560f943edbe3c2b032062f6673b13d3.tar.gz linux-4a4bac869560f943edbe3c2b032062f6673b13d3.tar.bz2 linux-4a4bac869560f943edbe3c2b032062f6673b13d3.zip | |
fbcon: fix integer overflow in fbcon_do_set_font
commit 1a194e6c8e1ee745e914b0b7f50fa86c89ed13fe upstream.
Fix integer overflow vulnerabilities in fbcon_do_set_font() where font
size calculations could overflow when handling user-controlled font
parameters.
The vulnerabilities occur when:
1. CALC_FONTSZ(h, pitch, charcount) performs h * pith * charcount
multiplication with user-controlled values that can overflow.
2. FONT_EXTRA_WORDS * sizeof(int) + size addition can also overflow
3. This results in smaller allocations than expected, leading to buffer
overflows during font data copying.
Add explicit overflow checking using check_mul_overflow() and
check_add_overflow() kernel helpers to safety validate all size
calculations before allocation.
Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 39b3cffb8cf3 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access")
Cc: George Kennedy <george.kennedy@oracle.com>
Cc: stable <stable@vger.kernel.org>
Cc: syzbot+38a3699c7eaf165b97a6@syzkaller.appspotmail.com
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Helge Deller <deller@gmx.de>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Qianqiang Liu <qianqiang.liu@163.com>
Cc: Shixiong Ou <oushixiong@kylinos.cn>
Cc: Kees Cook <kees@kernel.org>
Cc: <stable@vger.kernel.org> # v5.9+
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250912170023.3931881-1-samasth.norway.ananda@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/video/fbdev/core/fbcon.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 893fd66b5269..009b13cf6544 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2519,9 +2519,16 @@ static int fbcon_set_font(struct vc_data *vc, const struct console_font *font, if (fbcon_invalid_charcount(info, charcount)) return -EINVAL; - size = CALC_FONTSZ(h, pitch, charcount); + /* Check for integer overflow in font size calculation */ + if (check_mul_overflow(h, pitch, &size) || + check_mul_overflow(size, charcount, &size)) + return -EINVAL; + + /* Check for overflow in allocation size calculation */ + if (check_add_overflow(FONT_EXTRA_WORDS * sizeof(int), size, &size)) + return -EINVAL; - new_data = kmalloc(FONT_EXTRA_WORDS * sizeof(int) + size, GFP_USER); + new_data = kmalloc(size, GFP_USER); if (!new_data) return -ENOMEM; |