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authorzijun_hu <zijun_hu@htc.com>2016-10-05 21:30:24 +0800
committerTejun Heo <tj@kernel.org>2016-10-05 11:52:55 -0400
commit9b7396624a7b503220d85428654634b60762f2b0 (patch)
treefde5873a7ebf27bd57db430f3077d7e323eadd5f
parent93c76b6b2faaad7bfbc0cda840763aa4819ef26e (diff)
downloadlinux-9b7396624a7b503220d85428654634b60762f2b0.tar.bz2
mm/percpu.c: fix potential memory leakage for pcpu_embed_first_chunk()
in order to ensure the percpu group areas within a chunk aren't distributed too sparsely, pcpu_embed_first_chunk() goes to error handling path when a chunk spans over 3/4 VMALLOC area, however, during the error handling, it forget to free the memory allocated for all percpu groups by going to label @out_free other than @out_free_areas. it will cause memory leakage issue if the rare scene really happens, in order to fix the issue, we check chunk spanned area immediately after completing memory allocation for all percpu groups, we go to label @out_free_areas to free the memory then return if the checking is failed. in order to verify the approach, we dump all memory allocated then enforce the jump then dump all memory freed, the result is okay after checking whether we free all memory we allocate in this function. BTW, The approach is chosen after thinking over the below scenes - we don't go to label @out_free directly to fix this issue since we maybe free several allocated memory blocks twice - the aim of jumping after pcpu_setup_first_chunk() is bypassing free usable memory other than handling error, moreover, the function does not return error code in any case, it either panics due to BUG_ON() or return 0. Signed-off-by: zijun_hu <zijun_hu@htc.com> Tested-by: zijun_hu <zijun_hu@htc.com> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--mm/percpu.c36
1 files changed, 18 insertions, 18 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index e2737e56b017..255714302394 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1963,7 +1963,7 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
struct pcpu_alloc_info *ai;
size_t size_sum, areas_size;
unsigned long max_distance;
- int group, i, rc;
+ int group, i, highest_group, rc;
ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
cpu_distance_fn);
@@ -1979,7 +1979,8 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
goto out_free;
}
- /* allocate, copy and determine base address */
+ /* allocate, copy and determine base address & max_distance */
+ highest_group = 0;
for (group = 0; group < ai->nr_groups; group++) {
struct pcpu_group_info *gi = &ai->groups[group];
unsigned int cpu = NR_CPUS;
@@ -2000,6 +2001,21 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
areas[group] = ptr;
base = min(ptr, base);
+ if (ptr > areas[highest_group])
+ highest_group = group;
+ }
+ max_distance = areas[highest_group] - base;
+ max_distance += ai->unit_size * ai->groups[highest_group].nr_units;
+
+ /* warn if maximum distance is further than 75% of vmalloc space */
+ if (max_distance > VMALLOC_TOTAL * 3 / 4) {
+ pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
+ max_distance, VMALLOC_TOTAL);
+#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+ /* and fail if we have fallback */
+ rc = -EINVAL;
+ goto out_free_areas;
+#endif
}
/*
@@ -2024,24 +2040,8 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
}
/* base address is now known, determine group base offsets */
- i = 0;
for (group = 0; group < ai->nr_groups; group++) {
ai->groups[group].base_offset = areas[group] - base;
- if (areas[group] > areas[i])
- i = group;
- }
- max_distance = ai->groups[i].base_offset +
- ai->unit_size * ai->groups[i].nr_units;
-
- /* warn if maximum distance is further than 75% of vmalloc space */
- if (max_distance > VMALLOC_TOTAL * 3 / 4) {
- pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
- max_distance, VMALLOC_TOTAL);
-#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
- /* and fail if we have fallback */
- rc = -EINVAL;
- goto out_free;
-#endif
}
pr_info("Embedded %zu pages/cpu @%p s%zu r%zu d%zu u%zu\n",