On Mon, Apr 30, 2018 at 5:38 PM, Dilger, Andreas <andreas.dilger@xxxxxxxxx> wrote: > 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 > Thanks! I will re-submit the patch with the corrected commit message. Wenwen _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
