On Mon, Nov 25, 2024 at 08:29:10AM -0800, Dmitry Torokhov wrote: > On Mon, Nov 25, 2024 at 05:08:13PM +0200, Raag Jadav wrote: > > On Mon, Nov 25, 2024 at 09:49:22AM +0200, Andy Shevchenko wrote: > > > On Sun, Nov 24, 2024 at 07:03:36AM +0000, Dmitry Torokhov wrote: > > > > On Sun, Nov 24, 2024 at 01:35:23AM +0530, Raag Jadav wrote: ... > > > > > Introduce '_array' variant of devm_kmemdup() for the users which lack > > > > > multiplication overflow check. > > > > > > > > I am not sure that this new helper is needed. Unlike allocators for > > > > brand new objects, such as kmalloc_array(), devm_kmemdup() makes a copy > > > > of already existing object, which is supposed to be a valid object and > > > > therefore will have a reasonable size. So there should be no chance for > > > > hitting this overflow unless the caller is completely confused and calls > > > > devm_kmemdup() with random arguments (in which case all bets are off). > > > > > > Don't we want to have a code more robust even if all what you say applies? > > > Also this makes the call consistent with zillions of others from the alloc > > > family of calls in the Linux kernel. > > Having a clean API is fine, just do not bill it as something that is > "safer". As I mentioned, unlike other allocators this one is supposed to > operate with a valid source object and size passed to devm_kmemdup() > should not exceed the size of the source object. There is no chance of > overflowing. Agree. > > Agree. Although shooting in the foot is never the expectation, it is > > atleast better than having to debug such unexpected cases. > > Then maybe have a BUG() there instead of returning NULL? I know BUG()s > are frowned upon, but I think in this case overflow is really an > indicator of a hard error by the caller which is passing garbage > arguments to this function. > > Hm, I see we have kmemdup_array() already. Ok. How about making your > devm_kmemdup_array() be similar to kmemdup_array()? > > static inline void *devm_kmemdup_array(struct device *dev, const void *src, > size_t n, size_t size, gfp_t flags) > { > return devm_kmemdup(dev, src, size_mul(size, n), flags); > } > > This will trigger a warning on a too large order of allocation in > mm/page_alloc.c::__alloc_pages_noprof(). This is nice! I have overlooked that kmemdup_array() uses size_mul() instead of a check. Raag, can you rebuild your series on this? -- With Best Regards, Andy Shevchenko