From mboxrd@z Thu Jan 1 00:00:00 1970 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 2372E257C for ; Thu, 23 Feb 2023 13:08:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 802ADC433D2; Thu, 23 Feb 2023 13:08:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1677157680; bh=i37TLvNnEmaCtvbJVQ4tQ0P92FxYaxj2ZY3IXFgPfzI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RaykJ4AtYiTulG1VGseFV0Y+1ttJMbIowNGJIaw8O/WOWbDeyE7Zidvuss3zWRAxM v9sRE6/qHDIQUcuAQ01nig94//DMR8/ua15eYxKELgJugfDq1ybY8z+QwKbBkrEmrU /9ZgtkQQa2eF6F2GbD8Naou8OT68V2PU0Rh+oPg8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Theodore Tso , Eric Biggers , "Gustavo A. R. Silva" , Nathan Chancellor , Kees Cook , Eric Biggers Subject: [PATCH 5.10 24/25] ext4: Fix function prototype mismatch for ext4_feat_ktype Date: Thu, 23 Feb 2023 14:06:41 +0100 Message-Id: <20230223130427.880094473@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230223130426.817998725@linuxfoundation.org> References: <20230223130426.817998725@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Kees Cook commit 118901ad1f25d2334255b3d50512fa20591531cd upstream. With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed. ext4_feat_ktype was setting the "release" handler to "kfree", which doesn't have a matching function prototype. Add a simple wrapper with the correct prototype. This was found as a result of Clang's new -Wcast-function-type-strict flag, which is more sensitive than the simpler -Wcast-function-type, which only checks for type width mismatches. Note that this code is only reached when ext4 is a loadable module and it is being unloaded: CFI failure at kobject_put+0xbb/0x1b0 (target: kfree+0x0/0x180; expected type: 0x7c4aa698) ... RIP: 0010:kobject_put+0xbb/0x1b0 ... Call Trace: ext4_exit_sysfs+0x14/0x60 [ext4] cleanup_module+0x67/0xedb [ext4] Fixes: b99fee58a20a ("ext4: create ext4_feat kobject dynamically") Cc: Theodore Ts'o Cc: Eric Biggers Cc: stable@vger.kernel.org Build-tested-by: Gustavo A. R. Silva Reviewed-by: Gustavo A. R. Silva Reviewed-by: Nathan Chancellor Link: https://lore.kernel.org/r/20230103234616.never.915-kees@kernel.org Signed-off-by: Kees Cook Reviewed-by: Eric Biggers Link: https://lore.kernel.org/r/20230104210908.gonna.388-kees@kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/ext4/sysfs.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -487,6 +487,11 @@ static void ext4_sb_release(struct kobje complete(&sbi->s_kobj_unregister); } +static void ext4_feat_release(struct kobject *kobj) +{ + kfree(kobj); +} + static const struct sysfs_ops ext4_attr_ops = { .show = ext4_attr_show, .store = ext4_attr_store, @@ -501,7 +506,7 @@ static struct kobj_type ext4_sb_ktype = static struct kobj_type ext4_feat_ktype = { .default_groups = ext4_feat_groups, .sysfs_ops = &ext4_attr_ops, - .release = (void (*)(struct kobject *))kfree, + .release = ext4_feat_release, }; static struct kobject *ext4_root;