[PATCH] holepunch: fix mmap_sem i_mutex deadlock
sys_madvise has down_write of mmap_sem, then madvise_remove calls vmtruncate_range which takes i_mutex and i_alloc_sem: no, we can easily devise deadlocks from that ordering. madvise_remove drop mmap_sem while calling vmtruncate_range: luckily, since madvise_remove doesn't split or merge vmas, it's easy to handle this case with a NULL prev, without restructuring sys_madvise. (Though sad to retake mmap_sem when it's unlikely to be needed, and certainly down_read is sufficient for MADV_REMOVE, unlike the other madvices.) Signed-off-by: NHugh Dickins <hugh@veritas.com> Cc: Miklos Szeredi <mszeredi@suse.cz> Cc: Badari Pulavarty <pbadari@us.ibm.com> Cc: Nick Piggin <npiggin@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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