The following commit in -next:
commit 054620849110 ("mm/sparse.c: make sparse_init_one_section void and
remove check")
changed how the error handling in sparse_add_one_section() works.
Previously sparse_index_init() could return -EEXIST, and the function would
continue on happily. 'ret' would get unconditionally overwritten by the
result from sparse_init_one_section() and the error code after the 'out:'
label wouldn't be triggered.
With the above referenced commit, though, an -EEXIST error return from
sparse_index_init() now takes us through the function and into the error
case after 'out:'. This eventually causes a kernel BUG, probably because
we've just freed a memory section that we successfully set up and marked as
present:
BUG: unable to handle kernel paging request at ffffea0005000080
RIP: 0010:memmap_init_zone+0x154/0x1cf
Call Trace:
move_pfn_range_to_zone+0x168/0x180
devm_memremap_pages+0x29b/0x480
pmem_attach_disk+0x1ae/0x6c0 [nd_pmem]
? devm_memremap+0x79/0xb0
nd_pmem_probe+0x7e/0xa0 [nd_pmem]
nvdimm_bus_probe+0x6e/0x160 [libnvdimm]
driver_probe_device+0x310/0x480
__device_attach_driver+0x86/0x100
? __driver_attach+0x110/0x110
bus_for_each_drv+0x6e/0xb0
__device_attach+0xe2/0x160
device_initial_probe+0x13/0x20
bus_probe_device+0xa6/0xc0
device_add+0x41b/0x660
? lock_acquire+0xa3/0x210
nd_async_device_register+0x12/0x40 [libnvdimm]
async_run_entry_fn+0x3e/0x170
process_one_work+0x230/0x680
worker_thread+0x3f/0x3b0
kthread+0x12f/0x150
? process_one_work+0x680/0x680
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x3a/0x50
Fix this by clearing 'ret' back to 0 if sparse_index_init() returns
-EEXIST. This restores the previous behavior.
Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
---
mm/sparse.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/sparse.c b/mm/sparse.c
index 9574113fc745..d254bd2d3289 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -753,8 +753,12 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
* plus, it does a kmalloc
*/
ret = sparse_index_init(section_nr, pgdat->node_id);
- if (ret < 0 && ret != -EEXIST)
- return ret;
+ if (ret < 0) {
+ if (ret == -EEXIST)
+ ret = 0;
+ else
+ return ret;
+ }
memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, altmap);
if (!memmap)
return -ENOMEM;
--
2.14.4
