• Ming Lei's avatar
    lib/scatterlist.c: don't flush_kernel_dcache_page on slab page · 3d77b50c
    Ming Lei authored
    Commit b1adaf65 ("[SCSI] block: add sg buffer copy helper
    functions") introduces two sg buffer copy helpers, and calls
    flush_kernel_dcache_page() on pages in SG list after these pages are
    written to.
    
    Unfortunately, the commit may introduce a potential bug:
    
     - Before sending some SCSI commands, kmalloc() buffer may be passed to
       block layper, so flush_kernel_dcache_page() can see a slab page
       finally
    
     - According to cachetlb.txt, flush_kernel_dcache_page() is only called
       on "a user page", which surely can't be a slab page.
    
     - ARCH's implementation of flush_kernel_dcache_page() may use page
       mapping information to do optimization so page_mapping() will see the
       slab page, then VM_BUG_ON() is triggered.
    
    Aaro Koskinen reported the bug on ARM/kirkwood when DEBUG_VM is enabled,
    and this patch fixes the bug by adding test of '!PageSlab(miter->page)'
    before calling flush_kernel_dcache_page().
    Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
    Reported-by: default avatarAaro Koskinen <aaro.koskinen@iki.fi>
    Tested-by: default avatarSimon Baatz <gmbnomis@gmail.com>
    Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
    Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: <stable@vger.kernel.org>	[3.2+]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    3d77b50c
scatterlist.c 17.8 KB