From: Samasth Norway Ananda <samasth.norway.ananda@oracle.com> stable inclusion from stable-v5.10.245 commit 9c8ec14075c5317edd6b242f1be8167aa1e4e333 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ID22A7 CVE: CVE-2025-39967 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- 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@ora... Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- drivers/video/fbdev/core/fbcon.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 81bf4f7bd9e8..15d51e1baf74 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2547,9 +2547,16 @@ static int fbcon_set_font(struct vc_data *vc, 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; -- 2.34.1