Quoting J. Bruce Fields (bfields@xxxxxxxxxxxx): > Seems this isn't entirely obvious in the general case. In the specific I think the MKNOD part is (based on historical behavior as you suggested) obvious: both masks should include CAP_MKNOD and CAP_LINUX_IMMUTABLE. (references: http://lxr.linux.no/linux-old+v2.0.21/fs/ext2/ioctl.c#L60 for immutable and http://lxr.linux.no/linux-old+v2.0.21/fs/namei.c#L503 for mknod) -serge > case of nfsd, however, this is pretty obvious. So I'm inclined to > submit the following now (and leave it to be reverted by a later patch > if CAP_FS_MASK ends up including CAP_MKNOD, as seems likely). > > --b. > > commit 2ec8f8f0c0005ffe3cf93bbf3d9976de76cf4652 > Author: J. Bruce Fields <bfields@xxxxxxxxxxxxxx> > Date: Mon Mar 16 18:34:20 2009 -0400 > > nfsd: nfsd should drop CAP_MKNOD for non-root > > Since creating a device node is normally an operation requiring special > privilege, Igor Zhbanov points out that it is surprising (to say the > least) that a client can, for example, create a device node on a > filesystem exported with root_squash. > > So, make sure CAP_MKNOD is among the capabilities dropped when an nfsd > thread handles a request from a non-root user. > > Reported-by: Igor Zhbanov <izh1979@xxxxxxxxx> > Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx> > > diff --git a/include/linux/capability.h b/include/linux/capability.h > index 02bdb76..7824483 100644 > --- a/include/linux/capability.h > +++ b/include/linux/capability.h > @@ -393,8 +393,10 @@ struct cpu_vfs_cap_data { > # define CAP_FULL_SET ((kernel_cap_t){{ ~0, ~0 }}) > # define CAP_INIT_EFF_SET ((kernel_cap_t){{ ~CAP_TO_MASK(CAP_SETPCAP), ~0 }}) > # define CAP_FS_SET ((kernel_cap_t){{ CAP_FS_MASK_B0, CAP_FS_MASK_B1 } }) > -# define CAP_NFSD_SET ((kernel_cap_t){{ CAP_FS_MASK_B0|CAP_TO_MASK(CAP_SYS_RESOURCE), \ > - CAP_FS_MASK_B1 } }) > +# define CAP_NFSD_SET ((kernel_cap_t){{ CAP_FS_MASK_B0 \ > + | CAP_TO_MASK(CAP_SYS_RESOURCE) \ > + | CAP_TO_MASK(CAP_MKNOD), \ > + CAP_FS_MASK_B1 } }) > > #endif /* _KERNEL_CAPABILITY_U32S != 2 */ -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@xxxxxxxxxxxxx with the words "unsubscribe selinux" without quotes as the message.
