Hello, I'll fork it into a separate thread and Cc more MM people. sorry for top-posting. Minchan reported that doing copy_page() on a kmalloc(PAGE_SIZE) page with DEBUG_SLAB enabled can cause a memory corruption (See below or lkml.kernel.org/r/1492042622-12074-2-git-send-email-minchan@xxxxxxxxxx ) that's an interesting problem. arm64 copy_page(), for instance, wants src and dst to be page aligned, which is reasonable, while generic copy_page(), on the contrary, simply does memcpy(). there are, probably, other callpaths that do copy_page() on kmalloc-ed pages and I'm wondering if there is some sort of a generic fix to the problem. > > On (04/13/17 09:17), Minchan Kim wrote: > > > The copy_page is optimized memcpy for page-alinged address. > > > If it is used with non-page aligned address, it can corrupt memory which > > > means system corruption. With zram, it can happen with > > > > > > 1. 64K architecture > > > 2. partial IO > > > 3. slub debug > > > > > > Partial IO need to allocate a page and zram allocates it via kmalloc. > > > With slub debug, kmalloc(PAGE_SIZE) doesn't return page-size aligned > > > address. And finally, copy_page(mem, cmem) corrupts memory. > > > > which would be the case for many other copy_page() calls in the kernel. > > right? if so - should the fix be in copy_page() then? > > I thought about it but was not sure it's good idea by several reasons > (but don't want to discuss it in this thread). > > Anyway, it's stable stuff so I don't want to make the patch bloat. > If you believe it is right direction and valuable, you could be > a volunteer. :) -ss -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
