On Tue, Oct 29, 2013 at 12:20:05AM +0800, Ming Lei wrote: > Commit b1adaf65ba03([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(). > > Reported-by: Aaro Koskinen <[email protected]> > Cc: Russell King - ARM Linux <[email protected]> > Cc: [email protected] > Cc: Simon Baatz <[email protected]> > Cc: Will Deacon <[email protected]> > Cc: Aaro Koskinen <[email protected]> > Cc: Catalin Marinas <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: FUJITA Tomonori <[email protected]> > Cc: Tejun Heo <[email protected]> > Cc: "James E.J. Bottomley" <[email protected]> > Cc: Jens Axboe <[email protected]> > Signed-off-by: Ming Lei <[email protected]> > --- > lib/scatterlist.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index a685c8a..d16fa29 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -577,7 +577,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter) > miter->__offset += miter->consumed; > miter->__remaining -= miter->consumed; > > - if (miter->__flags & SG_MITER_TO_SG) > + if ((miter->__flags & SG_MITER_TO_SG) && > + !PageSlab(miter->page)) > flush_kernel_dcache_page(miter->page); > > if (miter->__flags & SG_MITER_ATOMIC) { > -- > 1.7.9.5 >
Tested-by: Simon Baatz <[email protected]> on top of 3.12-rc7 on Kirkwood with DEBUG_VM enabled. - Simon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
