On 03/07/2017 06:22 AM, Minchan Kim wrote: > Hello Johannes, > > On Mon, Mar 06, 2017 at 11:23:35AM +0100, Johannes Thumshirn wrote: >> zram can handle at most SECTORS_PER_PAGE sectors in a bio's bvec. When using >> the NVMe over Fabrics loopback target which potentially sends a huge bulk of >> pages attached to the bio's bvec this results in a kernel panic because of >> array out of bounds accesses in zram_decompress_page(). > > First of all, thanks for the report and fix up! > Unfortunately, I'm not familiar with that interface of block layer. > > It seems this is a material for stable so I want to understand it clear. > Could you say more specific things to educate me? > > What scenario/When/How it is problem? It will help for me to understand! > The problem is that zram as it currently stands can only handle bios where each bvec contains a single page (or, to be precise, a chunk of data with a length of a page).
This is not an automatic guarantee from the block layer (who is free to send us bios with arbitrary-sized bvecs), so we need to set the queue limits to ensure that. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking h...@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
