On Thu, 26 Sep 2019, Joe Perches wrote: > On Wed, 2019-09-25 at 14:50 -0700, Andrew Morton wrote: > > On Tue, 23 Jul 2019 06:51:36 -0700 Joe Perches <joe@xxxxxxxxxxx> wrote: > > > > > Several uses of strlcpy and strscpy have had defects because the > > > last argument of each function is misused or typoed. > > > > > > Add macro mechanisms to avoid this defect. > > > > > > stracpy (copy a string to a string array) must have a string > > > array as the first argument (dest) and uses sizeof(dest) as the > > > count of bytes to copy. > > > > > > These mechanisms verify that the dest argument is an array of > > > char or other compatible types like u8 or s8 or equivalent. > > > > > > A BUILD_BUG is emitted when the type of dest is not compatible. > > > > > > > I'm still reluctant to merge this because we don't have code in -next > > which *uses* it. You did have a patch for that against v1, I believe? > > Please dust it off and send it along? > > https://lore.kernel.org/lkml/CAHk-=wgqQKoAnhmhGE-2PBFt7oQs9LLAATKbYa573UO=DPBE0Q@xxxxxxxxxxxxxx/ > > I gave up, especially after the snark from Linus > where he wrote I don't understand this stuff. > > He's just too full of himself here merely using > argument from authority. > > Creating and using a function like copy_string with > both source and destination lengths specified is > is also potentially a large source of defects where > the stracpy macro atop strscpy does not have a > defect path other than the src not being a string > at all. > > I think the analysis of defects in string function > in the kernel is overly difficult today given the > number of possible uses of pointer and length in > strcpy/strncpy/strlcpy/stracpy. > > I think also that there is some sense in what he > wrote against the "word salad" use of str<foo>cpy, > but using stracpy as a macro when possible instead > of strscpy also makes the analysis of defects rather > simpler. > > The trivial script cocci I posted works well for the > simple cases. > > https://lore.kernel.org/cocci/66fcdbf607d7d0bea41edb39e5579d63b62b7d84.camel@xxxxxxxxxxx/ > > The more complicated cocci script Julia posted is > still not quite correct as it required intermediate > compilation for verification of specified lengths. The script works fine without compilation, but uses compilation as an extra sanity check. When there is only one possible declaration of a given buffer, then the compilation is not really needed. julia > > https://lkml.org/lkml/2019/7/25/1406 > > Tell me again if you still want it and maybe the > couple conversions that mm/ would get. > > via: > > $ spatch --all-includes --in-place -sp-file str.cpy.cocci mm > $ git diff --stat -p mm > -- > mm/dmapool.c | 2 +- > mm/zswap.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/dmapool.c b/mm/dmapool.c > index fe5d33060415..b3a4feb423f8 100644 > --- a/mm/dmapool.c > +++ b/mm/dmapool.c > @@ -158,7 +158,7 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, > if (!retval) > return retval; > > - strlcpy(retval->name, name, sizeof(retval->name)); > + stracpy(retval->name, name); > > retval->dev = dev; > > diff --git a/mm/zswap.c b/mm/zswap.c > index 08b6cefae5d8..c6cd38de185a 100644 > --- a/mm/zswap.c > +++ b/mm/zswap.c > @@ -533,7 +533,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor) > } > pr_debug("using %s zpool\n", zpool_get_type(pool->zpool)); > > - strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name)); > + stracpy(pool->tfm_name, compressor); > pool->tfm = alloc_percpu(struct crypto_comp *); > if (!pool->tfm) { > pr_err("percpu alloc failed\n"); > > > >