Re: [PATCH] 9p/xen: Fix end of loop tests for list_for_each_entry
From: asmadeus@codewreck.org
Date: 2021-07-25 20:47:03
Also in:
lkml
Harshvardhan Jha wrote on Sun, Jul 25, 2021 at 11:21:03PM +0530:
The list_for_each_entry() iterator, "priv" in this code, can never be NULL so the warning would never be printed.
hm? priv won't be NULL but priv->client won't be client, so it will return -EINVAL alright in practice? This does fix an invalid read after the list head, so there's a real bug, but the commit message needs fixing.
Signed-off-by: Harshvardhan Jha <redacted> --- From static analysis. Not tested.
+Stefano in To - I also can't test xen right now :/ This looks functional to me but if you have a bit of time to spare just a mount test can't hurt.
quoted hunk ↗ jump to hunk
--- net/9p/trans_xen.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c index f4fea28e05da..3ec1a51a6944 100644 --- a/net/9p/trans_xen.c +++ b/net/9p/trans_xen.c@@ -138,7 +138,7 @@ static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size) static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req) { - struct xen_9pfs_front_priv *priv = NULL; + struct xen_9pfs_front_priv *priv; RING_IDX cons, prod, masked_cons, masked_prod; unsigned long flags; u32 size = p9_req->tc.size;@@ -151,7 +151,7 @@ static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req) break; } read_unlock(&xen_9pfs_lock); - if (!priv || priv->client != client) + if (list_entry_is_head(priv, &xen_9pfs_devs, list)) return -EINVAL; num = p9_req->tc.tag % priv->num_rings;
-- Dominique