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net/9p: Check errno validity 

While working on a modified server I had the Linux clients crash
a few times. This lead me to find this:

Some error codes are directly extracted from the server replies.
A malformed server reply could contain an invalid error code, with a
very large value. If this value is then passed to ERR_PTR() it will
not be properly detected as an error code by IS_ERR() and as a result
the kernel will dereference an invalid pointer.

This patch tries to avoid this.

Signed-off-by: Simon Derr <simon.derr@bull.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This commit is contained in:
Simon Derr 2012-08-10 15:52:06 +02:00 committed by Eric Van Hensbergen
parent ba413ab2cc
commit 43def35c10
1 changed files with 16 additions and 2 deletions
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18
net/9p/client.c
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@ -76,6 +76,20 @@ inline int p9_is_proto_dotu(struct p9_client *clnt)
}
EXPORT_SYMBOL(p9_is_proto_dotu);
/*
* Some error codes are taken directly from the server replies,
* make sure they are valid.
*/
static int safe_errno(int err)
{
if ((err > 0) || (err < -MAX_ERRNO)) {
p9_debug(P9_DEBUG_ERROR, "Invalid error code %d\n", err);
return -EPROTO;
}
return err;
}
/* Interpret mount option for protocol version */
static int get_protocol_version(char *s)
{
@ -782,7 +796,7 @@ again:
return req;
reterr:
p9_free_req(c, req);
return ERR_PTR(err);
return ERR_PTR(safe_errno(err));
}
/**
@ -865,7 +879,7 @@ static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type,
return req;
reterr:
p9_free_req(c, req);
return ERR_PTR(err);
return ERR_PTR(safe_errno(err));
}
static struct p9_fid *p9_fid_create(struct p9_client *clnt)