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 693A53CF692; Wed, 22 Apr 2026 11:29:58 +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=1776857398; cv=none; b=kqaEeMYaCrmT5lYY4YSS/MNwciuRx9thBBWzspWyyY+qpvTdtbdr8qD5MjZe4C7/1/TBGvUOlKF4jdJNCgN6L4iwVQ78N468GO13sqVpstkxbd3q4p/SMWY0RsEGYplxj+SmHfpOIMKde+J3c0mVJBu0CDZoOLHjWL8F9SUf+/w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776857398; c=relaxed/simple; bh=cIJ29G+FMTvUgpAEP1ioMEAE8xKc9qyZE9tprcAxfDE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=Eg4aepIknFnk+jAvKU+RlTMlwoGdSkyOtK2SMYgyICXwjjCzxRm7RSkn51fhYkitsKu334ZLOIyAyeT2frMiDBM62fGBwl4MHAcZN6wHUZVcg8osNLRiHcOKGcS+7u3BFFalAr+D0f20htChkvNE9fdLDURIQ4r8ZjWI/RPGq/E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hWVKU+/w; 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="hWVKU+/w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5AFC9C2BCB4; Wed, 22 Apr 2026 11:29:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776857397; bh=cIJ29G+FMTvUgpAEP1ioMEAE8xKc9qyZE9tprcAxfDE=; h=From:Date:Subject:To:Cc:From; b=hWVKU+/wbGdcsYmm2gflVEUcbYok1xKtD2Nk4/rWJvhBYn0AkoxsSB5GPe9nEU35K +AlFnYGixX3wJDnPfsSo99UE79yXRhLnlt/+ewAcMjHJOUJKf6G025YFqMO2huxTCW it/Nkv00jxLwYKJREAI1mWZNDkHG19X8wTE7RA+g/VTNDCLZmFFXR2QSaHPwgzDMzW OaBi3ZE/pCAoEnL9F7SZOPGjWcVSrpNgSEAQwSRzXTT2ykW8p1SIOHA06kb39Rh5Eu RCBrwyTyjuBILJ0UmbjYjlFZoZxGECfK3cigz7xixUimNZaEU5rg480bQdQra4nFQR VDgXxBAnj9jxA== From: Jeff Layton Date: Wed, 22 Apr 2026 07:29:48 -0400 Subject: [PATCH] dcache: add extra sanity checks of the dentry in dentry_free() Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260422-dcache-warn-v1-1-50155e1b40b6@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDEyMj3ZTkxOSMVN3yxKI8XWPDpBRzi1RDi5RkYyWgjoKi1LTMCrBp0bG 1tQAc8rijXQAAAA== X-Change-ID: 20260422-dcache-warn-31bd78e18dc3 To: Alexander Viro , Christian Brauner , Jan Kara Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Layton X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=2294; i=jlayton@kernel.org; h=from:subject:message-id; bh=cIJ29G+FMTvUgpAEP1ioMEAE8xKc9qyZE9tprcAxfDE=; b=owEBbQKS/ZANAwAKAQAOaEEZVoIVAcsmYgBp6LExiDkVutYUx+LirKqgO02fWe61q3yGvNNUQ ySBEqLH7rCJAjMEAAEKAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCaeixMQAKCRAADmhBGVaC FYHeD/9Jg6pI9MW4L7Gw7SpO4pag5cGRGTzvoY40Q12Lxs0Zi2wNRhDOLgynz/ZJjK1WO/FXlrs VlqzX4XGa6uMDJwKFhG7FyU5VmNEJ6oUQ23gZ1rt4XGd1qBQYpTZQx+ceICwxm2RUOFmlNqumSs iiEkcrkVyGZ0BOOWk0iChKHyiO9w7dH+WrIZQjBUXqkxQRqAcOODpreodrIXSxKNGrYrrkUqyyV PaBc+avJ/pTyGSdOYs/jKLCITO4QV8lNdVPcmGTZAtbIybE99wbE0+MUK718rKVim5D9qynBE6M QcCTSZvgmDWe+62VTlAQ50MIEpPy/OUG8/tak8nvcckpGit8A8BUWnA+MNc3BLG2zq0GiLbenwA fyCqicehM9FDWs1lW8M3etPEU9wR5d+okap8rBIPQq5UBq0qDkVr+R1KgXKuwcEgZGmIeKXXAk7 LobhT9UPmgdRcKe8uxoZ/COzMyvs3Bgnmr5kIUPE6BH88dH60qEcasoqUHXw2g8GApw7oOrYoAH N1wKjE2mQxnso6lNjua9u6YerAMY3ssusDXLyhlzi/Z8pCj2C4+A6uVKrWpzUAc3iJwLVVM1sFf uS5QMeMyqTFXCLXR2iylAPOogVtiStWOdT0e1OS11Jae7Lt8/M8ihsOx7TenN0llZ7r3ZTDJUPt IkTcpX5r4bRit3w== X-Developer-Key: i=jlayton@kernel.org; a=openpgp; fpr=4BC0D7B24471B2A184EAF5D3000E684119568215 If d_flags isn't what we expect, then it's good to display it. Add a new DENTRY_WARN_ONCE() macro that also displays d_flags for the dentry. Change D_FLAG_VERIFY() to call that instead of a generic WARN_ON_ONCE(). Change the existing hlist_unhashed() check in dentry_free() to use the new macro, and add checks for other invariants of a dead dentry. Notably: 1) Ensure that DCACHE_LRU_LIST and DCACHE_SHRINK_LIST are not set. 2) Ensure that d_lockref is negative Signed-off-by: Jeff Layton --- While chatting with Al about this elusive UAF problem, we both noted that it would be nice to know what d_flags are when these warnings pop. This adds that, and checks for some other invariants in dentry_free(). --- fs/dcache.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 2c61aeea41f4..210df5c0a1f0 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -426,9 +426,16 @@ static inline void __d_clear_type_and_inode(struct dentry *dentry) this_cpu_inc(nr_dentry_negative); } +#define DENTRY_WARN_ONCE(condition, dentry) \ + WARN_ONCE((condition), "dentry=%p d_flags=0x%x\n", (dentry), (dentry)->d_flags) +#define D_FLAG_VERIFY(dentry, x) \ + DENTRY_WARN_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x), (dentry)) + static void dentry_free(struct dentry *dentry) { - WARN_ON(d_really_is_positive(dentry)); + DENTRY_WARN_ONCE(d_really_is_positive(dentry), dentry); + DENTRY_WARN_ONCE(dentry->d_lockref.count >= 0, dentry); + D_FLAG_VERIFY(dentry, 0); if (unlikely(dname_external(dentry))) { struct external_name *p = external_name(dentry); if (likely(atomic_dec_and_test(&p->count))) { @@ -495,7 +502,6 @@ static void dentry_unlink_inode(struct dentry * dentry) * These helper functions make sure we always follow the * rules. d_lock must be held by the caller. */ -#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x)) static void d_lru_add(struct dentry *dentry) { D_FLAG_VERIFY(dentry, 0); --- base-commit: 4ee64205ffaa587e8114d84a67ac721399ccb369 change-id: 20260422-dcache-warn-31bd78e18dc3 Best regards, -- Jeff Layton