On Fri, May 4, 2018 at 5:08 AM, Dilger, Andreas <andreas.dilger@xxxxxxxxx> wrote: > 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. > But, if the user uses such a struct, the second fetch won't be executed. This is a little bit different from using LOV_MAGIC_V3 firstly and then changing it to LOV_MAGIC_V1. Wenwen _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
