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Fri, 24 Jul 2026 14:46:58 -0700 (PDT) From: Fredric Cover To: sfrench@samba.org Cc: pc@manguebit.org, ronniesahlberg@gmail.com, sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com, linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org, Fredric Cover , stable@vger.kernel.org Subject: [PATCH v2 1/2] smb: client: harden DFS cache against invalid target hints Date: Fri, 24 Jul 2026 14:44:34 -0700 Message-ID: <20260724214435.1850384-2-fredric.cover.lkernel@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260724214435.1850384-1-fredric.cover.lkernel@gmail.com> References: <20260724023539.1596955-1-fredric.cover.lkernel@gmail.com> <20260724214435.1850384-1-fredric.cover.lkernel@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, get_tgt_name() returns ERR_PTR(-ENOENT) when ce->tgthint is NULL, and dfs_cache_noreq_update_tgthint() assumes ce->tgthint is always valid. In preparation for clearing ce->tgthint in free_tgts(), harden callers of get_tgt_name() against ERR_PTR results and harden dfs_cache_noreq_update_tgthint() against NULL pointer dereferences. Cc: stable@vger.kernel.org Signed-off-by: Fredric Cover --- fs/smb/client/dfs_cache.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/fs/smb/client/dfs_cache.c b/fs/smb/client/dfs_cache.c index 8cd93cd2f00f..c9ace4326a35 100644 --- a/fs/smb/client/dfs_cache.c +++ b/fs/smb/client/dfs_cache.c @@ -869,13 +869,22 @@ int dfs_cache_find(const unsigned int xid, struct cif= s_ses *ses, const struct nl goto out_free_path; } =20 - if (ref) - rc =3D setup_referral(path, ce, ref, get_tgt_name(ce)); - else + if (ref) { + char *target =3D get_tgt_name(ce); + + if (IS_ERR(target)) { + rc =3D PTR_ERR(target); + goto out_unlock; + } + rc =3D setup_referral(path, ce, ref, target); + } else { rc =3D 0; + } + if (!rc && tgt_list) rc =3D get_targets(ce, tgt_list); =20 +out_unlock: up_read(&htable_rw_lock); =20 out_free_path: @@ -915,10 +924,17 @@ int dfs_cache_noreq_find(const char *path, struct dfs= _info3_param *ref, goto out_unlock; } =20 - if (ref) - rc =3D setup_referral(path, ce, ref, get_tgt_name(ce)); - else + if (ref) { + char *target =3D get_tgt_name(ce); + + if (IS_ERR(target)) { + rc =3D PTR_ERR(target); + goto out_unlock; + } + rc =3D setup_referral(path, ce, ref, target); + } else { rc =3D 0; + } if (!rc && tgt_list) rc =3D get_targets(ce, tgt_list); =20 @@ -959,7 +975,8 @@ void dfs_cache_noreq_update_tgthint(const char *path, c= onst struct dfs_cache_tgt =20 t =3D READ_ONCE(ce->tgthint); =20 - if (unlikely(!strcasecmp(it->it_name, t->name))) + /* Check 't' in case ce->tgthint was cleared by free_tgts() */ + if (t && unlikely(!strcasecmp(it->it_name, t->name))) goto out_unlock; =20 list_for_each_entry(t, &ce->tlist, list) { --=20 2.53.0 From nobody Sat Jul 25 05:59:33 2026 Received: from mail-qt1-f176.google.com (mail-qt1-f176.google.com [209.85.160.176]) (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 266FD3812F6 for ; Fri, 24 Jul 2026 21:47:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Fri, 24 Jul 2026 14:47:04 -0700 (PDT) Received: from FredPC.lan ([2600:382:311b:26:c204:8bd0:9563:8b5f]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-529a29cf785sm7916771cf.21.2026.07.24.14.47.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jul 2026 14:47:03 -0700 (PDT) From: Fredric Cover To: sfrench@samba.org Cc: pc@manguebit.org, ronniesahlberg@gmail.com, sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com, linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org, Fredric Cover , stable@vger.kernel.org Subject: [PATCH v2 2/2] smb: client: clear ce->tgthint in free_tgts() Date: Fri, 24 Jul 2026 14:44:35 -0700 Message-ID: <20260724214435.1850384-3-fredric.cover.lkernel@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260724214435.1850384-1-fredric.cover.lkernel@gmail.com> References: <20260724023539.1596955-1-fredric.cover.lkernel@gmail.com> <20260724214435.1850384-1-fredric.cover.lkernel@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When free_tgts() frees all structures in ce->tlist, ce->tgthint is left pointing to one of the freed cache_dfs_tgt structures. If ce->tgthint is not reset before it is used later, it results in a use-after-free. Set ce->tgthint to NULL in free_tgts() after the elements are freed to reflect that no elements remain. Fixes: 54be1f6c1c37 ("cifs: Add DFS cache routines") Cc: stable@vger.kernel.org # depends on: smb: client: harden DFS cache agai= nst invalid target hints Signed-off-by: Fredric Cover --- fs/smb/client/dfs_cache.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/smb/client/dfs_cache.c b/fs/smb/client/dfs_cache.c index c9ace4326a35..86dba25b7a5a 100644 --- a/fs/smb/client/dfs_cache.c +++ b/fs/smb/client/dfs_cache.c @@ -122,6 +122,8 @@ static inline void free_tgts(struct cache_entry *ce) kfree(t->name); kfree(t); } + + WRITE_ONCE(ce->tgthint, NULL); } =20 static inline void flush_cache_ent(struct cache_entry *ce) --=20 2.53.0