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Message-ID: <CA+FuTSftgpOGxAxRE5u9o6gT_exaLtC2JkBz=iq21qe+tTTomA@mail.gmail.com> Date: Sun, 24 Oct 2021 09:51:35 -0400 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: Christophe JAILLET <christophe.jaillet@...adoo.fr> Cc: jeroendb@...gle.com, csully@...gle.com, awogbemila@...gle.com, davem@...emloft.net, kuba@...nel.org, bcf@...gle.com, gustavoars@...nel.org, edumazet@...gle.com, jfraker@...gle.com, yangchun@...gle.com, xliutaox@...gle.com, sagis@...gle.com, lrizzo@...gle.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org Subject: Re: [PATCH] gve: Fix a possible invalid memory access On Sun, Oct 24, 2021 at 7:52 AM Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote: > > It is spurious to allocate a bitmap for 'num_qpls' bits and record the > size of this bitmap with another value. > > 'qpl_map_size' is used in 'drivers/net/ethernet/google/gve/gve.h' with > 'find_[first|next]_zero_bit()'. > So, it looks that memory after the allocated 'qpl_id_map' could be > scanned. find_first_zero_bit takes a length argument in bits: /** * find_first_zero_bit - find the first cleared bit in a memory region * @addr: The address to start the search at * @size: The maximum number of bits to search qpl_map_size is passed to find_first_zero_bit. It does seem roundabout to compute first the number of longs needed to hold num_qpl bits BITS_TO_LONGS(num_qpls) then again compute the number of bits in this buffer * sizeof(unsigned long) * BITS_PER_BYTE Which will simply be num_qpls again. But, removing BITS_PER_BYTE does not arrive at the right number. > > Remove the '* BITS_PER_BYTE' to have allocation and length be the same. > > Fixes: f5cedc84a30d ("gve: Add transmit and receive support") > Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr> > --- > This patch is completely speculative and un-tested! > You'll be warned. > --- > drivers/net/ethernet/google/gve/gve_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c > index 7647cd05b1d2..19fe9e9b62f5 100644 > --- a/drivers/net/ethernet/google/gve/gve_main.c > +++ b/drivers/net/ethernet/google/gve/gve_main.c > @@ -866,7 +866,7 @@ static int gve_alloc_qpls(struct gve_priv *priv) > } > > priv->qpl_cfg.qpl_map_size = BITS_TO_LONGS(num_qpls) * > - sizeof(unsigned long) * BITS_PER_BYTE; > + sizeof(unsigned long); > priv->qpl_cfg.qpl_id_map = kvcalloc(BITS_TO_LONGS(num_qpls), > sizeof(unsigned long), GFP_KERNEL); > if (!priv->qpl_cfg.qpl_id_map) { > -- > 2.30.2 >
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