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authorDavid Howells <dhowells@redhat.com>2010-01-15 17:01:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-01-16 12:15:40 -0800
commit81759b5b221107488bda99fe7beeb7b734f61133 (patch)
tree2ca1207d4ae5d6bbdc49db727a35b22a502fc76f /include
parentefc1a3b16930c41d64ffefde16b87d82f603a8a0 (diff)
downloadlinux-linaro-android-81759b5b221107488bda99fe7beeb7b734f61133.tar.gz
nommu: fix race between ramfs truncation and shared mmap
Fix the race between the truncation of a ramfs file and an attempt to make a shared mmap of region of that file. The problem is that do_mmap_pgoff() calls f_op->get_unmapped_area() to verify that the file region is made of contiguous pages and to find its base address - but there isn't any locking to guarantee this region until vma_prio_tree_insert() is called by add_vma_to_mm(). Note that moving the functionality into f_op->mmap() doesn't help as that is also called before vma_prio_tree_insert(). Instead make ramfs_nommu_check_mappings() grab nommu_region_sem whilst it does its checks. This means that this function will wait whilst mmaps take place. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Greg Ungerer <gerg@snapgear.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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