On Apr 29, 2018, at 07:20, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, Apr 28, 2018 at 04:04:25PM +0000, Dilger, Andreas wrote: >> On Apr 27, 2018, at 17:45, Wenwen Wang <wang6495@xxxxxxx> wrote: >>> [PATCH] staging: luster: llite: fix potential missing-check bug when copying lumv >> >> (typo) s/luster/lustre/ >> >>> In ll_dir_ioctl(), the object lumv3 is firstly copied from the user space >>> using Its address, i.e., lumv1 = &lumv3. If the lmm_magic field of lumv3 is >>> LOV_USER_MAGIV_V3, lumv3 will be modified by the second copy from the user >> >> (typo) s/MAGIV/MAGIC/ >> >>> space. The second copy is necessary, because the two versions (i.e., >>> lov_user_md_v1 and lov_user_md_v3) have different data formats and lengths. >>> However, given that the user data resides in the user space, a malicious >>> user-space process can race to change the data between the two copies. By >>> doing so, the attacker can provide a data with an inconsistent version, >>> e.g., v1 version + v3 data. This can lead to logical errors in the >>> following execution in ll_dir_setstripe(), which performs different actions >>> according to the version specified by the field lmm_magic. >> >> This isn't a serious bug in the end. The LOV_USER_MAGIC_V3 check just copies >> a bit more data from userspace (the lmm_pool field). It would be more of a >> problem if the reverse was possible (copy smaller V1 buffer, but change the >> magic to LOV_USER_MAGIC_V3 afterward), but this isn't possible since the second >> copy is not done if there is a V1 magic. If the user changes from V3 magic >> to V1 in a racy manner it means less data will be used than copied, which >> is harmless. >> >>> This patch rechecks the version field lmm_magic in the second copy. If the >>> version is not as expected, i.e., LOV_USER_MAGIC_V3, an error code will be >>> returned: -EINVAL. >> >> This isn't a bad idea in any case, since it verifies the data copied from >> userspace is still valid. > > So you agree with this patch? Or do not? > > confused, I don't think it fixes a real bug, but it makes the code a bit more clear, so I'm OK to land it (with minor corrections to commit message per above). Cheers, Andreas -- Andreas Dilger Lustre Principal Architect Intel Corporation _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
