damos_new_filter() is returning a damos_filter struct without
initializing its ->list field. And the users of the function uses the
struct without initializing the field. As a result, uninitialized
memory access error is possible. Actually, a kernel NULL pointer
dereference BUG can be triggered using DAMON user-space tool, like
below.
# damo start --damos_action stat --damos_filter anon matching
# damo tune --damos_action stat --damos_filter anon matching --damos_filter anon nomatching
# dmesg
[...]
[ 36.908136] BUG: kernel NULL pointer dereference, address: 0000000000000008
[ 36.910483] #PF: supervisor write access in kernel mode
[ 36.912238] #PF: error_code(0x0002) - not-present page
[ 36.913415] PGD 0 P4D 0
[ 36.913978] Oops: 0002 [#1] PREEMPT SMP PTI
[ 36.914878] CPU: 32 PID: 1335 Comm: kdamond.0 Not tainted 6.5.0-rc3-mm-unstable-damon+ #1
[ 36.916621] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 36.919051] RIP: 0010:damos_destroy_filter (include/linux/list.h:114 include/linux/list.h:137 include/linux/list.h:148 mm/damon/core.c:345 mm/damon/core.c:355)
[...]
[ 36.938247] Call Trace:
[ 36.938721] <TASK>
[...]
[ 36.950064] ? damos_destroy_filter (include/linux/list.h:114 include/linux/list.h:137 include/linux/list.h:148 mm/damon/core.c:345 mm/damon/core.c:355)
[ 36.950883] ? damon_sysfs_set_scheme_filters.isra.0 (mm/damon/sysfs-schemes.c:1573)
[ 36.952019] damon_sysfs_set_schemes (mm/damon/sysfs-schemes.c:1674 mm/damon/sysfs-schemes.c:1686)
[ 36.952875] damon_sysfs_apply_inputs (mm/damon/sysfs.c:1312 mm/damon/sysfs.c:1298)
[ 36.953757] ? damon_pa_check_accesses (mm/damon/paddr.c:168 mm/damon/paddr.c:179)
[ 36.954648] damon_sysfs_cmd_request_callback (mm/damon/sysfs.c:1329 mm/damon/sysfs.c:1359)
[...]
The first patch of this patchset fixes the bug by initializing the field in
damos_new_filter(). The second patch adds a unit test for the problem.
Note that the second patch Cc stable@ without Fixes: tag, since it would
be better to be ingested together for avoiding any future regression.
SeongJae Park (2):
mm/damon/core: initialize damo_filter->list from damos_new_filter()
mm/damon/core-test: add a test for damos_new_filter()
mm/damon/core-test.h | 13 +++++++++++++
mm/damon/core.c | 1 +
2 files changed, 14 insertions(+)
--
2.25.1
damos_new_filter() is not initializing the list field of newly allocated
filter object. However, DAMON sysfs interface and DAMON_RECLAIM are not
initializing it after calling damos_new_filter(). As a result,
accessing uninitialized memory is possible. Actually, adding multiple
DAMOS filters via DAMON sysfs interface caused NULL pointer
dereferencing. Initialize the field just after the allocation from
damos_new_filter().
Fixes: 98def236f63c ("mm/damon/core: implement damos filter")
Cc: [email protected] # 6.3.x-
Signed-off-by: SeongJae Park <[email protected]>
---
mm/damon/core.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 91cff7f2997e..eb9580942a5c 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -273,6 +273,7 @@ struct damos_filter *damos_new_filter(enum damos_filter_type type,
return NULL;
filter->type = type;
filter->matching = matching;
+ INIT_LIST_HEAD(&filter->list);
return filter;
}
--
2.25.1