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 A5A0D36D511 for ; Thu, 20 Nov 2025 20:23:21 +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=1763670201; cv=none; b=o5yCeXFPrwgTA2bM+EVk06gJ4A9qQgCToBV1RxGvGLOzALMcSPVfAMQAPUPV0JexI7C36opEoMBT6fdlufrFYw0aQtKZEm5ACLwoOvuUnFUl8AfuixrdbTx2T/aKGNNLqhvUp1Wt/GAMg7oYJo8cRAprUbML4m7m+nyaxzIHj1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763670201; c=relaxed/simple; bh=9oXKKf6bMIAszvdTeriKX/qVxVbYKuAMcrnlrs+kMm0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Iz4CN3JhXAG+zS5r05Fvxibrj2IQ4d5n4Li/JJVXvjh5tYyepg7pBYwdSQVNNmBlB+UMYb3cAJKrEX1fkfBXcI3iUUy3fYdXgcQJWiHN4s5gA4phIJxzS7YwDNQxItqHqRA2KYs9ETvBi/XZwdR1rbUclk/obaMMtlfeDP+B/qI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dF0cSBrU; 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="dF0cSBrU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8625C4CEF1; Thu, 20 Nov 2025 20:23:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763670201; bh=9oXKKf6bMIAszvdTeriKX/qVxVbYKuAMcrnlrs+kMm0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dF0cSBrUEOt8GHqH6WG9EmOsSKLShe98fFgUfNZa/BS7lbZTT/rC+hpQtMhNaKiT4 jq0Lf4+AfVBd5hyfzfcXhmAFEiYcevE+Jx9sot54I5kCvW8uQrWJUsxNEAqs52GuRr ul52+qI6F0yDPPJdaxvC72QCU8moxdlE3YK35d7qyvswgP8rvYjqYm+wYSqFmb/5kq m2Z+DNKEzTytSPsoyizulVFxplJoDaWGC/L4WI9V1kNjMPaFqDnlIg5WOSXuRFdgF+ WANhaScC8ndCG+4SFXBB8iUcC8j5mbdBLobWLRxdYFtFMCpn8OnBs6+HXT1bXibig1 nVXdC6MMohhiA== From: Sasha Levin To: stable@vger.kernel.org Cc: Wei Yang , Al Viro , Christian Brauner , wangzijie , Alexey Dobriyan , Andrew Morton , Sasha Levin Subject: [PATCH 5.4.y] fs/proc: fix uaf in proc_readdir_de() Date: Thu, 20 Nov 2025 15:23:17 -0500 Message-ID: <20251120202317.2307846-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025112019-mantra-unwind-1db7@gregkh> References: <2025112019-mantra-unwind-1db7@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Wei Yang [ Upstream commit 895b4c0c79b092d732544011c3cecaf7322c36a1 ] Pde is erased from subdir rbtree through rb_erase(), but not set the node to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE() set the erased node to EMPTY, then pde_subdir_next() will return NULL to avoid uaf access. We found an uaf issue while using stress-ng testing, need to run testcase getdent and tun in the same time. The steps of the issue is as follows: 1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current pde is tun3; 2) in the [time windows] unregister netdevice tun3 and tun2, and erase them from rbtree. erase tun3 first, and then erase tun2. the pde(tun2) will be released to slab; 3) continue to getdent process, then pde_subdir_next() will return pde(tun2) which is released, it will case uaf access. CPU 0 | CPU 1 ------------------------------------------------------------------------- traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2 sys_getdents64() | iterate_dir() | proc_readdir() | proc_readdir_de() | snmp6_unregister_dev() pde_get(de); | proc_remove() read_unlock(&proc_subdir_lock); | remove_proc_subtree() | write_lock(&proc_subdir_lock); [time window] | rb_erase(&root->subdir_node, &parent->subdir); | write_unlock(&proc_subdir_lock); read_lock(&proc_subdir_lock); | next = pde_subdir_next(de); | pde_put(de); | de = next; //UAF | rbtree of dev_snmp6 | pde(tun3) / \ NULL pde(tun2) Link: https://lkml.kernel.org/r/20251025024233.158363-1-albin_yang@163.com Signed-off-by: Wei Yang Cc: Al Viro Cc: Christian Brauner Cc: wangzijie Cc: Alexey Dobriyan Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- fs/proc/generic.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 372b4dad4863e..c4a7d96787f36 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -671,6 +671,12 @@ void pde_put(struct proc_dir_entry *pde) } } +static void pde_erase(struct proc_dir_entry *pde, struct proc_dir_entry *parent) +{ + rb_erase(&pde->subdir_node, &parent->subdir); + RB_CLEAR_NODE(&pde->subdir_node); +} + /* * Remove a /proc entry and free it if it's not currently in use. */ @@ -689,7 +695,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) de = pde_subdir_find(parent, fn, len); if (de) { - rb_erase(&de->subdir_node, &parent->subdir); + pde_erase(de, parent); if (S_ISDIR(de->mode)) { parent->nlink--; } @@ -727,13 +733,13 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) write_unlock(&proc_subdir_lock); return -ENOENT; } - rb_erase(&root->subdir_node, &parent->subdir); + pde_erase(root, parent); de = root; while (1) { next = pde_subdir_first(de); if (next) { - rb_erase(&next->subdir_node, &de->subdir); + pde_erase(next, de); de = next; continue; } -- 2.51.0