Re: [PATCH 3/5] mm/sparse: fix possible memory leak
From: Michal Hocko <hidden>
Date: 2012-06-25 15:48:53
On Sat 23-06-12 23:52:54, Gavin Shan wrote:
With CONFIG_SPARSEMEM_EXTREME, the root memory section descriptors are allocated by slab or bootmem allocator. Also, the descriptors might have been allocated and initialized by others. However, the memory chunk allocated in current implementation wouldn't be put into the available pool if others have allocated memory chunk for that.
Who is others? I assume that we can race in hotplug because other than that this is an early initialization code. How can others race?
The patch introduces addtional function sparse_index_free() to deallocate the memory chunk if the root memory section descriptor has been initialized by others.
The fix itself looks correct but I do not see how this happens...
quoted hunk ↗ jump to hunk
Signed-off-by: Gavin Shan <redacted> --- mm/sparse.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)diff --git a/mm/sparse.c b/mm/sparse.c index ce50c8b..bae8f2d 100644 --- a/mm/sparse.c +++ b/mm/sparse.c@@ -86,6 +86,22 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid) return section; } +static void noinline __init_refok sparse_index_free(struct mem_section *section, + int nid) +{ + unsigned long size = SECTIONS_PER_ROOT * + sizeof(struct mem_section); + + if (!section) + return; + + if (slab_is_available()) + kfree(section); + else + free_bootmem_node(NODE_DATA(nid), + virt_to_phys(section), size); +} + static int __meminit sparse_index_init(unsigned long section_nr, int nid) { static DEFINE_SPINLOCK(index_init_lock);@@ -113,6 +129,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid) mem_section[root] = section; out: spin_unlock(&index_init_lock); + if (ret == -EEXIST) + sparse_index_free(section, nid);
Maybe a generic if (ret) would be more appropriate.
+ return ret; } #else /* !SPARSEMEM_EXTREME */ -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
-- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>