Messages in this thread | | | Date | Fri, 12 Feb 2021 15:12:16 +0100 | From | Miquel Raynal <> | Subject | Re: [PATCH] mtd: physmap: physmap-bt1-rom: Fix unintentional stack access |
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Hi Gustavo,
"Gustavo A. R. Silva" <gustavoars@kernel.org> wrote on Fri, 12 Feb 2021 04:40:22 -0600:
> Cast &data to (char *) in order to avoid unintentionally accessing > the stack. > > Notice that data is of type u32, so any increment to &data > will be in the order of 4-byte chunks, and this piece of code > is actually intended to be a byte offset.
I don't have the same reading. I don't say that Coverity report is wrong, but let's discuss this a bit further.
Given that &data is of type u32 *, you say that "&data + shift" produces increments of 4-bytes, ie. we would access "&data + 4 * shift"? Because I don't think this is the case (again, I may be wrong).
I'm sure this would be the case if we dereferenced data like data[shift] though, but in this case I don't see what this cast is fixing. Can you enlighten me?
Could the out-of-bounds warning come from the fact that shift might be bigger than the data array spread?
> Fixes: b3e79e7682e0 ("mtd: physmap: Add Baikal-T1 physically mapped ROM support") > Addresses-Coverity-ID: 1497765 ("Out-of-bounds access") > Cc: stable@vger.kernel.org > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > drivers/mtd/maps/physmap-bt1-rom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/mtd/maps/physmap-bt1-rom.c b/drivers/mtd/maps/physmap-bt1-rom.c > index a35450002284..58782cfaf71c 100644 > --- a/drivers/mtd/maps/physmap-bt1-rom.c > +++ b/drivers/mtd/maps/physmap-bt1-rom.c > @@ -79,7 +79,7 @@ static void __xipram bt1_rom_map_copy_from(struct map_info *map, > if (shift) { > chunk = min_t(ssize_t, 4 - shift, len); > data = readl_relaxed(src - shift); > - memcpy(to, &data + shift, chunk); > + memcpy(to, (char *)&data + shift, chunk); > src += chunk; > to += chunk; > len -= chunk;
Thanks, Miquèl
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