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9p/xen: fix check for xenbus_read error in front_probe

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[ Upstream commit 2f9ad0ac947ccbe3ffe7c6229c9330f2a7755f64 ]

If the xen bus exists but does not expose the proper interface, it is
possible to get a non-zero length but still some error, leading to
strcmp failing trying to load invalid memory addresses e.g.
fffffffffffffffe.

There is then no need to check length when there is no error, as the
xenbus driver guarantees that the string is nul-terminated.

Link: http://lkml.kernel.org/r/1534236007-10170-1-git-send-email-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Dominique Martinet 2018-08-14 02:43:48 +00:00 committed by Greg Kroah-Hartman
parent a8782ce026
commit f8bc5f1a3a
1 changed files with 2 additions and 2 deletions
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4
net/9p/trans_xen.c
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@ -391,8 +391,8 @@ static int xen_9pfs_front_probe(struct xenbus_device *dev,
unsigned int max_rings, max_ring_order, len = 0;
versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
if (!len)
return -EINVAL;
if (IS_ERR(versions))
return PTR_ERR(versions);
if (strcmp(versions, "1")) {
kfree(versions);
return -EINVAL;