I can see there are two problems, First: In kernel/sys.c:2117 capable(CAP_SYS_RESOURCE), seems that ns_capable should be used to check capability against user namespace, instead of init_user_ns. Because a process in a user namespace may call prctl system call and this should be checked against their user namespace capability instead of init_user_ns capability.
Second: They should both require CAP_SYS_RESOURCE or CAP_SYS_ADMIN, is there any particular reasons for requiring different privilege? > On Sep 25, 2018, at 2:34 PM, Cyrill Gorcunov <gorcu...@gmail.com> wrote: > > On Tue, Sep 25, 2018 at 07:37:45PM +0200, Greg KH wrote: >> On Tue, Sep 25, 2018 at 01:26:55PM -0400, Tong Zhang wrote: >>> Kernel Version: 4.18.5 >>> >>> Problem Description: >>> >>> We discovered inconsistent check when using prctl_set_mm_exe_file(), which >>> is used to setup exe file link. >>> >>> It is required to have capable(CAP_SYS_RESOURCE) in prctl_set_mm(). >>> while ns_capable(CAP_SYS_ADMIN) in prctl_set_mm_map(). >>> >>> There are two differences: >>> 1)requiring capability from: user namespace, init namespace. >>> 2)capability bit required is different >> >> Can you submit a patch showing what you think is the correct fix here? > > It is done this way on purpose. The prctl_set_mm_map is a complex call > which carries a bunch of parameters and allowed if you're inside user-ns > admin, > in turn prctl_set_mm allows to modify settings one by one. So no, it is not > an error but rather call specifics.
