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, greg k-h _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
