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net: Fix undefined behavior in netdev name allocation

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Cited commit removed the strscpy() call and kept the snprintf() only.

It is common to use 'dev->name' as the format string before a netdev is
registered, this results in 'res' and 'name' pointers being equal.
According to POSIX, if copying takes place between objects that overlap
as a result of a call to sprintf() or snprintf(), the results are
undefined.

Add back the strscpy() and use 'buf' as an intermediate buffer.

Fixes: 7ad17b04dc ("net: trust the bitmap in __dev_alloc_name()")
Cc: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gal Pressman 2023-11-14 09:56:18 +02:00 committed by David S. Miller
parent efc0c8363b
commit 674e318089
1 changed files with 3 additions and 1 deletions
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4
net/core/dev.c
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@ -1119,7 +1119,9 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
if (i == max_netdevices)
return -ENFILE;
snprintf(res, IFNAMSIZ, name, i);
/* 'res' and 'name' could overlap, use 'buf' as an intermediate buffer */
strscpy(buf, name, IFNAMSIZ);
snprintf(res, IFNAMSIZ, buf, i);
return i;
}