On Mon 23-09-19 15:36:12, Andrew Morton wrote: > From: Alastair D'Silva <[email protected]> > Subject: mm/memory_hotplug.c: add a bounds check to > check_hotplug_memory_range() > > Patch series "Add bounds check for Hotplugged memory", v3. > > This series adds bounds checks for hotplugged memory, ensuring that it is > within the physically addressable range (for platforms that define > MAX_(POSSIBLE_)PHYSMEM_BITS. > > This allows for early failure, rather than attempting to access bogus > section numbers. > > > This patch (of 2): > > On PowerPC, the address ranges allocated to OpenCAPI LPC memory are > allocated from firmware. These address ranges may be higher than what > older kernels permit, as we increased the maximum permissable address in > commit 4ffe713b7587 ("powerpc/mm: Increase the max addressable memory to > 2PB"). It is possible that the addressable range may change again in the > future. > > In this scenario, we end up with a bogus section returned from > __section_nr (see the discussion on the thread "mm: Trigger bug on if a > section is not found in __section_nr"). > > Adding a check here means that we fail early and have an opportunity to > handle the error gracefully, rather than rumbling on and potentially > accessing an incorrect section. > > Further discussion is also on the thread ("powerpc: Perform a bounds check > in arch_add_memory"). > > David said: > > : I guess checking for address space wrapping would be overkill. This > : change makes sense for architecture-independent device drivers that make > : use of the add/remove memory infrastructure (e.g., virtio-mem I am working > : on).
Isn't this rushed a bit? I've had a review feedback just yesterday http://lkml.kernel.org/r/[email protected] and had some concerns. > Link: http://lkml.kernel.org/r/[email protected] > Signed-off-by: Alastair D'Silva <[email protected]> > Reviewed-by: David Hildenbrand <[email protected]> > Cc: Oscar Salvador <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Pavel Tatashin <[email protected]> > Cc: Dan Williams <[email protected]> > Cc: Wei Yang <[email protected]> > Cc: Qian Cai <[email protected]> > Cc: Jason Gunthorpe <[email protected]> > Cc: Logan Gunthorpe <[email protected]> > Cc: Ira Weiny <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > --- > > include/linux/memory_hotplug.h | 1 + > mm/memory_hotplug.c | 13 ++++++++++++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > --- > a/include/linux/memory_hotplug.h~memory_hotplug-add-a-bounds-check-to-check_hotplug_memory_range > +++ a/include/linux/memory_hotplug.h > @@ -110,6 +110,7 @@ extern void __online_page_increment_coun > extern void __online_page_free(struct page *page); > > extern int try_online_node(int nid); > +int check_hotplug_memory_addressable(u64 start, u64 size); > > extern int arch_add_memory(int nid, u64 start, u64 size, > struct mhp_restrictions *restrictions); > --- > a/mm/memory_hotplug.c~memory_hotplug-add-a-bounds-check-to-check_hotplug_memory_range > +++ a/mm/memory_hotplug.c > @@ -1023,6 +1023,17 @@ int try_online_node(int nid) > return ret; > } > > +int check_hotplug_memory_addressable(u64 start, u64 size) > +{ > +#ifdef MAX_PHYSMEM_BITS > + if ((start + size - 1) >> MAX_PHYSMEM_BITS) > + return -E2BIG; > +#endif > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(check_hotplug_memory_addressable); > + > static int check_hotplug_memory_range(u64 start, u64 size) > { > /* memory range must be block size aligned */ > @@ -1033,7 +1044,7 @@ static int check_hotplug_memory_range(u6 > return -EINVAL; > } > > - return 0; > + return check_hotplug_memory_addressable(start, size); > } > > static int online_memory_block(struct memory_block *mem, void *arg) > _ -- Michal Hocko SUSE Labs
