On Thu, Dec 18, 2014 at 8:59 AM, H. Peter Anvin <h...@zytor.com> wrote: > On 12/18/2014 03:16 AM, tip-bot for Andy Lutomirski wrote: >> Commit-ID: 3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0 >> Gitweb: >> http://git.kernel.org/tip/3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0 >> Author: Andy Lutomirski <l...@amacapital.net> >> AuthorDate: Wed, 17 Dec 2014 14:48:30 -0800 >> Committer: Ingo Molnar <mi...@kernel.org> >> CommitDate: Thu, 18 Dec 2014 12:12:26 +0100 >> >> x86/tls: Don't validate lm in set_thread_area() after all >> >> It turns out that there's a lurking ABI issue. GCC, when >> compiling this in a 32-bit program: >> >> struct user_desc desc = { >> .entry_number = idx, >> .base_addr = base, >> .limit = 0xfffff, >> .seg_32bit = 1, >> .contents = 0, /* Data, grow-up */ >> .read_exec_only = 0, >> .limit_in_pages = 1, >> .seg_not_present = 0, >> .useable = 0, >> }; >> >> will leave .lm uninitialized. This means that anything in the >> kernel that reads user_desc.lm for 32-bit tasks is unreliable. >> > > No, it won't. However, if you initialize this dynamically field by > field rather than as an initializer, then you are correct. >
I tried the code above in function scope. --Andy > -hpa > -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
