3.2.67-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Konstantin Khlebnikov <[email protected]> commit b800c91a0517071156e772d4fb329ad33590da62 upstream. Fix for BUG_ON(anon_vma->degree) splashes in unlink_anon_vmas() ("kernel BUG at mm/rmap.c:399!") caused by commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy") Anon_vma_clone() is usually called for a copy of source vma in destination argument. If source vma has anon_vma it should be already in dst->anon_vma. NULL in dst->anon_vma is used as a sign that it's called from anon_vma_fork(). In this case anon_vma_clone() finds anon_vma for reusing. Vma_adjust() calls it differently and this breaks anon_vma reusing logic: anon_vma_clone() links vma to old anon_vma and updates degree counters but vma_adjust() overrides vma->anon_vma right after that. As a result final unlink_anon_vmas() decrements degree for wrong anon_vma. This patch assigns ->anon_vma before calling anon_vma_clone(). Signed-off-by: Konstantin Khlebnikov <[email protected]> Reported-and-tested-by: Chris Clayton <[email protected]> Reported-and-tested-by: Oded Gabbay <[email protected]> Reported-and-tested-by: Chih-Wei Huang <[email protected]> Acked-by: Rik van Riel <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Daniel Forrest <[email protected]> Cc: Michal Hocko <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> [bwh: Backported to 3.2: vma_adjust() didn't use a variable to propagate the error code from anon_vma_clone(); change that at the same time] Signed-off-by: Ben Hutchings <[email protected]> --- --- a/mm/mmap.c +++ b/mm/mmap.c @@ -537,9 +537,14 @@ again: remove_next = 1 + (end > next-> * shrinking vma had, to cover any anon pages imported. */ if (exporter && exporter->anon_vma && !importer->anon_vma) { - if (anon_vma_clone(importer, exporter)) - return -ENOMEM; + int error; + importer->anon_vma = exporter->anon_vma; + error = anon_vma_clone(importer, exporter); + if (error) { + importer->anon_vma = NULL; + return error; + } } } -- 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/
