On Thu, Jun 05, 2014 at 06:40:36AM +0200, Michael Kerrisk (man-pages) wrote: > On 06/05/2014 01:31 AM, Dave Jones wrote: > > I just noticed that trinity was freaking out in places when mmap was > > returning zero. This surprised me, because I had the mmap_min_addr > > sysctl set to 64k, so it wasn't a MAP_FIXED mapping that did it. > > > > There's no mention of this return value in the man page, so I dug > > into the kernel code, and it appears that we do.. > > > > sys_mmap > > vm_mmap_pgoff > > security_mmap_file > > ima_file_mmap <- returns 0 if not PROT_EXEC > > > > and then the 0 gets propagated up as a retval all the way to userspace. > > > > It smells to me like we might be violating a standard or two here, and > > instead of 0 ima should be returning -Esomething > > > > thoughts? > > Seems like either EACCESS or ENOTSUP is appropriate; here's the pieces > from POSIX: > > EACCES The fildes argument is not open for read, regardless of > the protection specified, or fildes is not open for > write and PROT_WRITE was specified for a MAP_SHARED type > mapping. > > ENOTSUP > The implementation does not support the combination > of accesses requested in the prot argument. > > ENOTSUP seems to be more appropriate in my reading of the above, though > I'd somehow more have expected EACCES. I just realised that this affects even kernels with CONFIG_IMA unset, because there we just do 'return 0' unconditionally. Also, it appears that kernels with CONFIG_SECURITY unset will also return a zero for the same reason. This is kind of a mess, and has been that way for a long time. Fixing this will require user-visible breakage, but in this case I think it's justified as there's no way an app can do the right thing if it gets a 0 back. Linus ? Dave -- 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>