mm/damon/core: validate damos_quota_goal->nid for node_memcg_{used,free}_bp

Users can set damos_quota_goal->nid with arbitrary value for
node_memcg_{used,free}_bp.  But DAMON core is using those for NODE-DATA()
without a validation of the value.  This can result in out of bounds
memory access.  The issue can actually triggered using DAMON user-space
tool (damo), like below.

    $ sudo mkdir /sys/fs/cgroup/foo
    $ sudo ./damo start --damos_action stat --damos_quota_interval 1s \
            --damos_quota_goal node_memcg_used_bp 50% -1 /foo
    $ sudo dmseg
    [...]
    [  524.181426] Unable to handle kernel paging request at virtual address 0000000000002c00

Fix this issue by adding the validation of the given node id.  If an
invalid node id is given, it returns 0% for used memory ratio, and 100%
for free memory ratio.

Link: https://lore.kernel.org/20260329043902.46163-3-sj@kernel.org
Fixes: b74a120bcf50 ("mm/damon/core: implement DAMOS_QUOTA_NODE_MEMCG_USED_BP")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.19.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 9a848d7647ef9e80d65c57c5d683d07320a1c8ab..19642c175568905720f0e6cf8bbf6f3e0381dd05 100644 (file)
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2251,6 +2251,13 @@ static unsigned long damos_get_node_memcg_used_bp(
        unsigned long used_pages, numerator;
        struct sysinfo i;
 
+       if (invalid_mem_node(goal->nid)) {
+               if (goal->metric == DAMOS_QUOTA_NODE_MEMCG_USED_BP)
+                       return 0;
+               else    /* DAMOS_QUOTA_NODE_MEMCG_FREE_BP */
+                       return 10000;
+       }
+
        memcg = mem_cgroup_get_from_id(goal->memcg_id);
        if (!memcg) {
                if (goal->metric == DAMOS_QUOTA_NODE_MEMCG_USED_BP)