From nobody Wed Dec 17 08:43:59 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E5CE25E836; Fri, 9 May 2025 20:06:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746821211; cv=none; b=He+R67R1Y2yFR1GE0UE4YjsK42M+vJQ8LufZsH1fYOW+IW98bP94t1HQ6e+I57xQvTfm5PaEZWoXe6OHGAn5eZWwV+LfE1DT1MN016SOCEVjHUs4PQVC3I8BmZtiyFxPyOaBlWfz3Ohni1lyOgfjeY+CLzq9BfFUnl50HUzEZoQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746821211; c=relaxed/simple; bh=c4N2IUsmCh9moub2+ZGNMBv0CyfWrRcXPTvqAC6Ij/I=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=rGAE/rpiyqlm4cG7jEhKnMmSAh37aIsqSMIyC3l+vpgpCJVU29ikvNTgY0WwFfGKnWDgt1bKHp5H80iEqLxy+2OlkzX8vCireSdGLi0juH+w8UlMGAFOD4pEAhUZR3BqMITQLWKMnzg4aHgHwHsg6pATeuIZS1UB6FYQsLIwrWo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iy/5oKN4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iy/5oKN4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04EB6C4CEE4; Fri, 9 May 2025 20:06:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746821211; bh=c4N2IUsmCh9moub2+ZGNMBv0CyfWrRcXPTvqAC6Ij/I=; h=From:To:Cc:Subject:Date:From; b=iy/5oKN4Rax6mwtekgtc7DQfTrvQ+wam5Jjx0PiEo57N2FQa4laN6F5Pf713nTxcz rJEKhMVmFHqunx+dD0tttYsmVTr3ljhtZkRRXt72Eyp6MN40bBWGnd7jPE51VFcuy0 i7gZuoE0yo8pyIk39tDuTrZhCRcj6Eef1sSRKhrUiN8a5ZXpazJ7IgDWPySCEmQLHJ MPbITL1LhxUGGm/K+byLzshRh6tfymDBT3+MV8td9nOUqPPHF2aV8LZdCkhjTvjYoq T1y0I6GYGXjkCfNWD6FfzmSHmMSfr9Cf/S1pIjYJdyfeipJ60e9WNd90d6m0jzRCif kAwjMTPHPtD2g== From: Kees Cook To: Simona Vetter Cc: Kees Cook , syzbot+a7d4444e7b6e743572f7@syzkaller.appspotmail.com, Helge Deller , Greg Kroah-Hartman , "Jiri Slaby (SUSE)" , Javier Martinez Canillas , Shixiong Ou , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Qianqiang Liu , Jocelyn Falempe , Zsolt Kajtar , linux-kernel@vger.kernel.org, syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com, linux-hardening@vger.kernel.org Subject: [PATCH] fbdev: fbcon: Make sure modelist not set on unregistered console Date: Fri, 9 May 2025 13:06:47 -0700 Message-Id: <20250509200643.work.355-kees@kernel.org> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2305; i=kees@kernel.org; h=from:subject:message-id; bh=c4N2IUsmCh9moub2+ZGNMBv0CyfWrRcXPTvqAC6Ij/I=; b=owGbwMvMwCVmps19z/KJym7G02pJDBlyCWH//WaueRBfJHD5a+nhDd/L42/f/L542tUJ0+wrn q/LdFl3oKOUhUGMi0FWTJElyM49zsXjbXu4+1xFmDmsTCBDGLg4BWAiy3IY/vsXvG2+e+HLYqtZ s3c+nt0XKsTc77J8XhOHfXjeZU7Ody4M/2v/VTEwFcQLZcqcWP5U1fes1kHGJ0HbGN4e2f3j5/e p/rwA X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It looks like attempting to write to the "store_modes" sysfs node will run afoul of unregistered consoles: UBSAN: array-index-out-of-bounds in drivers/video/fbdev/core/fbcon.c:122:28 index -1 is out of range for type 'fb_info *[32]' ... fbcon_info_from_console+0x192/0x1a0 drivers/video/fbdev/core/fbcon.c:122 fbcon_new_modelist+0xbf/0x2d0 drivers/video/fbdev/core/fbcon.c:3048 fb_new_modelist+0x328/0x440 drivers/video/fbdev/core/fbmem.c:673 store_modes+0x1c9/0x3e0 drivers/video/fbdev/core/fbsysfs.c:113 dev_attr_store+0x55/0x80 drivers/base/core.c:2439 static struct fb_info *fbcon_registered_fb[FB_MAX]; ... static signed char con2fb_map[MAX_NR_CONSOLES]; ... static struct fb_info *fbcon_info_from_console(int console) ... return fbcon_registered_fb[con2fb_map[console]]; If con2fb_map contains a -1 things go wrong here. Instead, return NULL, as callers of fbcon_info_from_console() are trying to compare against existing "info" pointers, so error handling should kick in correctly. Reported-by: syzbot+a7d4444e7b6e743572f7@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/679d0a8f.050a0220.163cdc.000c.GAE@googl= e.com/ Signed-off-by: Kees Cook --- Cc: Simona Vetter Cc: Helge Deller Cc: Greg Kroah-Hartman Cc: "Jiri Slaby (SUSE)" Cc: Javier Martinez Canillas Cc: Shixiong Ou Cc: Cc: --- drivers/video/fbdev/core/fbcon.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fb= con.c index ac3c99ed92d1..2df48037688d 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -117,9 +117,14 @@ static signed char con2fb_map_boot[MAX_NR_CONSOLES]; =20 static struct fb_info *fbcon_info_from_console(int console) { + signed char fb; WARN_CONSOLE_UNLOCKED(); =20 - return fbcon_registered_fb[con2fb_map[console]]; + fb =3D con2fb_map[console]; + if (fb < 0 || fb >=3D ARRAY_SIZE(fbcon_registered_fb)) + return NULL; + + return fbcon_registered_fb[fb]; } =20 static int logo_lines; --=20 2.34.1