• Linus Torvalds's avatar
    x86: fix SMAP in 32-bit environments · de9e478b
    Linus Torvalds authored
    In commit 11f1a4b9 ("x86: reorganize SMAP handling in user space
    accesses") I changed how the stac/clac instructions were generated
    around the user space accesses, which then made it possible to do
    batched accesses efficiently for user string copies etc.
    
    However, in doing so, I completely spaced out, and didn't even think
    about the 32-bit case.  And nobody really even seemed to notice, because
    SMAP doesn't even exist until modern Skylake processors, and you'd have
    to be crazy to run 32-bit kernels on a modern CPU.
    
    Which brings us to Andy Lutomirski.
    
    He actually tested the 32-bit kernel on new hardware, and noticed that
    it doesn't work.  My bad.  The trivial fix is to add the required
    uaccess begin/end markers around the raw accesses in <asm/uaccess_32.h>.
    
    I feel a bit bad about this patch, just because that header file really
    should be cleaned up to avoid all the duplicated code in it, and this
    commit just expands on the problem.  But this just fixes the bug without
    any bigger cleanup surgery.
    Reported-and-tested-by: default avatarAndy Lutomirski <luto@kernel.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    de9e478b
uaccess_32.h 6.09 KB