On May 3, 2018, at 22:19, Wenwen Wang <wang6495@xxxxxxx> wrote: > > On Tue, May 1, 2018 at 3:46 AM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote: >> On Mon, Apr 30, 2018 at 05:56:10PM -0500, Wenwen Wang wrote: >>> 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 part is misleading. The fix is to improve readability and make >> static checkers happy. You're over dramatizing it to make people think >> it has a security impact when it doesn't. >> >> If the user wants to specify v1 data they can just say that on the first >> read. They don't need to do funny tricks and race between the two >> reads. It's allowed. >> >> In other words this allows the user to do something in a very >> complicated way which they are already allowed to do in a very simple >> straight forward way. >> >> regards, >> dan carpenter > > Thanks for your comment, Dan! How about this: > > 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. The current kernel > can handle such inconsistent data. But, it may pose a potential > security risk for future implementations. Also, to improve code > readability and make static analysis tools happy, which will warn > about read-verify-re-read type bugs, this issue should be fixed. There is nothing preventing the user from using struct lov_mds_md_v3 but filling in lmm_magic = LOV_MAGIC_V1 from the beginning, no need for a race. Cheers, Andreas -- Andreas Dilger Lustre Principal Architect Intel Corporation _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
