From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f176.google.com (mail-pf1-f176.google.com [209.85.210.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 482F83148C5 for ; Tue, 5 May 2026 09:52:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777974733; cv=none; b=Cds0hhxGLtxcxzKagnuyweZhUE6Gml+qmXBx59XH6+3ZS/lqvVeBVrOkGOGm1lC0q464bdXz80hb9aefjvgMGyNAoastk+WuP8xsl2BjgSw9GJm9f/YFjNGLEfdFGAzAMZfcXmKWMFV0CE6uoZzpCvbhRC1+dPMn3GLChPegtC8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777974733; c=relaxed/simple; bh=C50xHnLVbEOK7GneCLj+4ihK+Y3olQywB6A6iuQURfI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ttrLDCb6WCO/gPc8CCSzgWuswrPJ+/ElKi1sRixFydnu8kbFagAHNoBN/Mh8d7mxUN5107od2MDBgfWqHmWX0CW1Its3uY2YEMeJL95DZM15GVA9MghZD/ASaroEQqLiO1Kap6krqjJMnTs23wU2iL6yAezGgJ7H51/1rNRAjzA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=E5M8cRIY; arc=none smtp.client-ip=209.85.210.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="E5M8cRIY" Received: by mail-pf1-f176.google.com with SMTP id d2e1a72fcca58-835c98b659eso1358333b3a.0 for ; Tue, 05 May 2026 02:52:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777974731; x=1778579531; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=gkwo6P8gTQNfH4qEff3exRmXn3jFDhuKToYPFVQ+fSY=; b=E5M8cRIYB5EJgB2ElL8MPi5KXc2vbg/iWSxShbusnjLs8fazyyeYpyYFplcsjlZ/s9 pEMg27Fy+iylmqGUbhK6QBKgDZ9QR5JaRDEvvSHFaVJe3QXDoPj5wL5CRBAbvBF4TmGn I9GSe0LbhvOG/wpgOWKZCIyW7Ngb/1Os3nLb8tvTHfw8mktRQTFKN+C/fJeRpP7WedEK vfh53dx+brc+eJiOe8oXY9UJlbYvQiAIBNgfmCLHDOG6ilJOH2bO1ViUDgt3l2NCHFU3 5/TLBVLlys5JRwlmR9+JAcb+oueUgAQfO55Ch8FCc0+A3V9zyVv9EOssCuz5LmMVzNsk i31w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777974732; x=1778579532; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gkwo6P8gTQNfH4qEff3exRmXn3jFDhuKToYPFVQ+fSY=; b=qjVXoclqosIJiQ7pCcSErBi+H8gkein542KiflbndC0ZMzMqjs/B1lMuQUSYQke88p NpLMzAyv6q3s0tjoJSfn2ZsvS6b0hPj2VzyJRDvxq4413eRABHfwnDxPlz/Lb4o2HbBh VgnaiRxgAuJytVbb2EAcIJUC9WRtV4Cs63baTGRSy4w+0gvlXZWT3UJYwi1ZnRFAERKB RkiAx8zfYi1hxMm6F+YvY8RSpBMZGtZQVsQxzXvblYj9Wk+az27pHAIN04+hFM5H8OCy 0QkIk/FAe4FYYUdJbfPXmibmY3FnDhsPkrVEU6gXy9QoBhNwIVr+bV9RWeq1mjD9kK0j JRmw== X-Forwarded-Encrypted: i=1; AFNElJ+OpWgWUq5RJs2wvy5ocwHqrhe1+x2QvCt+0Xncj0Q8LlYKKdq2jkcZwBdQsBduTFWFb1i9FIQAfL9m52y8@vger.kernel.org X-Gm-Message-State: AOJu0YzCxUuQNbskLhkAm/hAvR0sKNJd3y+E3OuJMMXpVWJu3i0nQVeR JPYRAOGhWdp+9SzmOOTFP2R/8yk/EqGsLUuuMchpHLPuA/AIPNJ2laPfeQ6Uk8zmAPA= X-Gm-Gg: AeBDiesOoDlzReaQQmKJP6IZhh8/0C5ehGl8jBEs2AHjTG3sIfP3Cb558j+CVR1zYIF X7v7PEeWzHMr5d0CoCoeK7XNVApfIjVCKlutfWaI1fFYR8JhnK8szkzq7JpnZO15QERX9yhjx4A xNhaXN+MldiEiX3TVaj1sn0GLwo0rE4ZQfpGbSwyuAZ8rVj5p5l2Ag8NLJxjOX5qYRaoKC2xfXl 47027CefGGdkt4NX7Af7rReBwstJgDgKyT+EstGqaGScf4aYsNh/4H+iNGbSaKO6OA9UBZeKz9x 0obGP9hA9/jrz2I0xGASUzKcHAAJcU2huQ2uiflAYiI8nKstMnZEjYTPwUOTpOkcoF3XMpDyVVf NHgJuqbccF54oCsr2OsSofiTc0MJAnUZdU8YrD2kAkk+AyEQfeDIR88F0KTcmUeGeEUGPB9EYsh GfOz97UI4TIi8YL69mL9PqoJ+6lbNRijP1tJ78Jc3T X-Received: by 2002:a05:6a00:14ca:b0:82f:721f:10ea with SMTP id d2e1a72fcca58-8352d1bf331mr13683369b3a.18.1777974731611; Tue, 05 May 2026 02:52:11 -0700 (PDT) Received: from vini ([2401:4900:8fc8:907b:6dbd:bd6e:9d0b:e8cf]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83965d38ab5sm2125855b3a.26.2026.05.05.02.52.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 May 2026 02:52:11 -0700 (PDT) From: Vineet Agarwal To: viro@zeniv.linux.org.uk Cc: brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Vineet Agarwal , syzbot Subject: [PATCH] fs/namespace: fix NULL pointer dereference in do_lock_mount() Date: Tue, 5 May 2026 15:21:31 +0530 Message-ID: <20260505095156.178351-1-agarwal.vineet2006@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Syzkaller reported a NULL pointer dereference in do_lock_mount() when calling inode_lock() on a dentry without an associated inode. where_to_mount() may return a negative dentry (without an inode) due to concurrent unlink or mount changes. The current code does not validate this before calling inode_lock(), leading to a crash. Fix this by checking dentry and dentry->d_inode before acquiring the inode lock. Reported-by: syzbot Closes: https://syzkaller.appspot.com/ Signed-off-by: Vineet Agarwal --- fs/namespace.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index fe919abd2f01..b1dccdf06836 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2760,6 +2760,17 @@ static void do_lock_mount(const struct path *path, } } + if (unlikely(!dentry || !dentry->d_inode)) { + err = -ENOENT; + if (&m->mnt != path->mnt) { + if (dentry) + dput(dentry); + mntput(&m->mnt); + } + res->parent = ERR_PTR(err); + return; + } + inode_lock(dentry->d_inode); namespace_lock(); -- 2.54.0