Hi Ronnie, Ronnie Sahlberg <lsahlber@xxxxxxxxxx> writes: > Steve, All, > > I think smb3-encryption has been broken for quite a while (forver?) > when we configure the kernel with CONFIG_DEBUG_SG="y". > > The problem is that with these extra checks, we can no longer pass a pointer > to a buffer that is allocated off the stack safely to sg_set_buf() as this > function will BUG_ON. It seems to me this sg_set_buf() is quite restrictive. Is it an actual bug to pass stack buffers or does it become one only if this debug thing is set? IIUC it's the latter. > We have a lot of places where cifs.ko does indeed pass a pointer to a > stack object to this function :-( and this patch will fix all the instances > I could find so far. Switching that many stack buffers to heap doesn't sound like a good idea, especially in hot paths :( pros: * we can use this scatter-gather table debug thing (how?). cons: * makes the code more complex: memory management in C is error-prone as you all know (memory leaks, use-after-free, extra error code paths to add if allocation fails, etc) * slower: heap allocation is not free (altho we should probably measure instead of speculate) I'd like to know more about this debug feature because I'm not sure why there is this requirement. In any case thanks for finding and looking at this. Cheers, -- Aurélien Aptel / SUSE Labs Samba Team GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3 SUSE Linux GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
