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authorHugh Dickins <hugh@veritas.com>2007-10-29 21:37:20 (GMT)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-30 15:06:55 (GMT)
commit487e9bf25cbae11b131d6a14bdbb3a6a77380837 (patch)
tree0b6666750274aadd22b29b1282aa779831976ca1 /mm/swap.c
parent8bca44bbd39007065cc6a4e3a50201475629a6cf (diff)
downloadlinux-fsl-qoriq-487e9bf25cbae11b131d6a14bdbb3a6a77380837.tar.xz
fix tmpfs BUG and AOP_WRITEPAGE_ACTIVATE
It's possible to provoke unionfs (not yet in mainline, though in mm and some distros) to hit shmem_writepage's BUG_ON(page_mapped(page)). I expect it's possible to provoke the 2.6.23 ecryptfs in the same way (but the 2.6.24 ecryptfs no longer calls lower level's ->writepage). This came to light with the recent find that AOP_WRITEPAGE_ACTIVATE could leak from tmpfs via write_cache_pages and unionfs to userspace. There's already a fix (e423003028183df54f039dfda8b58c49e78c89d7 - writeback: don't propagate AOP_WRITEPAGE_ACTIVATE) in the tree for that, and it's okay so far as it goes; but insufficient because it doesn't address the underlying issue, that shmem_writepage expects to be called only by vmscan (relying on backing_dev_info capabilities to prevent the normal writeback path from ever approaching it). That's an increasingly fragile assumption, and ramdisk_writepage (the other source of AOP_WRITEPAGE_ACTIVATEs) is already careful to check wbc->for_reclaim before returning it. Make the same check in shmem_writepage, thereby sidestepping the page_mapped BUG also. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: Erez Zadok <ezk@cs.sunysb.edu> Cc: <stable@kernel.org> Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap.c')
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