From: Chen Ridong <chenridong@huawei.com> mainline inclusion from mainline-v6.19 commit 43151f812886be1855d2cba059f9c93e4729460b category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/8422 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- An issue was triggered: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 15 UID: 0 PID: 658 Comm: bash Tainted: 6.19.0-rc6-next-2026012 Tainted: [O]=OOT_MODULE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), RIP: 0010:strcmp+0x10/0x30 RSP: 0018:ffffc900017f7dc0 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888107cd4358 RDX: 0000000019f73907 RSI: ffffffff82cc381a RDI: 0000000000000000 RBP: ffff8881016bef0d R08: 000000006c0e7145 R09: 0000000056c0e714 R10: 0000000000000001 R11: ffff888107cd4358 R12: 0007ffffffffffff R13: ffff888101399200 R14: ffff888100fcb360 R15: 0007ffffffffffff CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000105c79000 CR4: 00000000000006f0 Call Trace: <TASK> dmemcg_limit_write.constprop.0+0x16d/0x390 ? __pfx_set_resource_max+0x10/0x10 kernfs_fop_write_iter+0x14e/0x200 vfs_write+0x367/0x510 ksys_write+0x66/0xe0 do_syscall_64+0x6b/0x390 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f42697e1887 It was trriggered setting max without limitation, the command is like: "echo test/region0 > dmem.max". To fix this issue, add check whether options is valid after parsing the region_name. Fixes: b168ed458dde ("kernel/cgroup: Add "dmem" memory accounting cgroup") Cc: stable@vger.kernel.org # v6.14+ Signed-off-by: Chen Ridong <chenridong@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Liu Kai <liukai284@huawei.com> --- kernel/cgroup/dmem.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c index 951954ef9ba7..fc67efa8e1a9 100644 --- a/kernel/cgroup/dmem.c +++ b/kernel/cgroup/dmem.c @@ -699,6 +699,9 @@ static ssize_t dmemcg_limit_write(struct kernfs_open_file *of, if (!region_name[0]) continue; + if (!options || !*options) + return -EINVAL; + rcu_read_lock(); region = dmemcg_get_region_by_name(region_name); rcu_read_unlock(); -- 2.34.1