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Tue, 24 Mar 2026 08:30:32 -0700 (PDT) From: Eric-Terminal To: asmadeus@codewreck.org, ericvh@kernel.org, lucho@ionkov.net Cc: stefano.stabellini@amd.com, v9fs@lists.linux.dev, linux-kernel@vger.kernel.org, Yufan Chen Subject: [PATCH v3 1/2] 9p/trans_xen: make cleanup idempotent after dataring alloc errors Date: Tue, 24 Mar 2026 23:30:22 +0800 Message-ID: <20260324153023.86853-2-ericterminal@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260324153023.86853-1-ericterminal@gmail.com> References: <20260324153023.86853-1-ericterminal@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3464; i=ericterminal@gmail.com; h=from:subject; bh=vDNsz/omUMmP3CEetrmU1J5yJISS/nuy98ia+ZC4Yh4=; b=owGbwMvMwCXWM/dCzeS3H+sZT6slMWQeWqup5XD67uNZ+3kEygTn/5jXPf/RBxHWc/9zl+u4y c5r2bfBrWMiC4MYF4OlmCLL3f/75uZ63ZpznftwLswcViaQIdIiDQxAwMLAl5uYV2qkY6Rnqm2o Z2ikY6BjzMDFKQBTXbyckeH+2XsLvjlGSr7pWGT1ZA33V+FQlkfz6s/cnMH7ucki1bGB4Z9awql U3Rg7wQ0b8v+qTf3gee+q8I9+M/beugd/Z/zMV+YGAA== X-Developer-Key: i=ericterminal@gmail.com; a=openpgp; fpr=DDFFBE9D6D4ADA9CD70BC36D8C9DD07C93EDF17F Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Yufan Chen xen_9pfs_front_alloc_dataring() tears down resources on failure but leaves ring fields stale. If xen_9pfs_front_init() later jumps to the common error path, xen_9pfs_front_free() may touch the same resources again, causing duplicate/invalid gnttab_end_foreign_access() calls and potentially dereferencing a freed intf pointer. Initialize dataring sentinels before allocation, gate teardown on those sentinels, and clear ref/intf/data/irq immediately after each release. This keeps cleanup idempotent for partially initialized rings and prevents repeated teardown during init failure handling. Signed-off-by: Yufan Chen --- v3: - Split from mixed series into a dedicated 9p/trans_xen series. - No functional changes since v2. net/9p/trans_xen.c | 51 +++++++++++++++++++++++++++++++++------------- diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c index 47af5a10e..85b9ebfaa 100644 --- a/net/9p/trans_xen.c +++ b/net/9p/trans_xen.c @@ -283,25 +283,33 @@ static void xen_9pfs_front_free(struct xen_9pfs_front= _priv *priv) =20 cancel_work_sync(&ring->work); =20 - if (!priv->rings[i].intf) + if (!ring->intf) break; - if (priv->rings[i].irq > 0) - unbind_from_irqhandler(priv->rings[i].irq, ring); - if (priv->rings[i].data.in) { - for (j =3D 0; - j < (1 << priv->rings[i].intf->ring_order); + if (ring->irq >=3D 0) { + unbind_from_irqhandler(ring->irq, ring); + ring->irq =3D -1; + } + if (ring->data.in) { + for (j =3D 0; j < (1 << ring->intf->ring_order); j++) { grant_ref_t ref; =20 - ref =3D priv->rings[i].intf->ref[j]; + ref =3D ring->intf->ref[j]; gnttab_end_foreign_access(ref, NULL); + ring->intf->ref[j] =3D INVALID_GRANT_REF; } - free_pages_exact(priv->rings[i].data.in, - 1UL << (priv->rings[i].intf->ring_order + - XEN_PAGE_SHIFT)); + free_pages_exact(ring->data.in, + 1UL << (ring->intf->ring_order + + XEN_PAGE_SHIFT)); + ring->data.in =3D NULL; + ring->data.out =3D NULL; + } + if (ring->ref !=3D INVALID_GRANT_REF) { + gnttab_end_foreign_access(ring->ref, NULL); + ring->ref =3D INVALID_GRANT_REF; } - gnttab_end_foreign_access(priv->rings[i].ref, NULL); - free_page((unsigned long)priv->rings[i].intf); + free_page((unsigned long)ring->intf); + ring->intf =3D NULL; } kfree(priv->rings); } @@ -334,6 +342,12 @@ static int xen_9pfs_front_alloc_dataring(struct xenbus= _device *dev, int ret =3D -ENOMEM; void *bytes =3D NULL; =20 + ring->intf =3D NULL; + ring->data.in =3D NULL; + ring->data.out =3D NULL; + ring->ref =3D INVALID_GRANT_REF; + ring->irq =3D -1; + init_waitqueue_head(&ring->wq); spin_lock_init(&ring->lock); INIT_WORK(&ring->work, p9_xen_response); @@ -379,9 +393,18 @@ static int xen_9pfs_front_alloc_dataring(struct xenbus= _device *dev, for (i--; i >=3D 0; i--) gnttab_end_foreign_access(ring->intf->ref[i], NULL); free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT)); + ring->data.in =3D NULL; + ring->data.out =3D NULL; + } + if (ring->ref !=3D INVALID_GRANT_REF) { + gnttab_end_foreign_access(ring->ref, NULL); + ring->ref =3D INVALID_GRANT_REF; + } + if (ring->intf) { + free_page((unsigned long)ring->intf); + ring->intf =3D NULL; } - gnttab_end_foreign_access(ring->ref, NULL); - free_page((unsigned long)ring->intf); + ring->irq =3D -1; return ret; } =20 --=20 2.47.3