From: Baokun Li libaokun1@huawei.com
commit 0129ab1f268b6cf88825eae819b9b84aa0a85634 upstream.
Hulk robot reported a kmemleak problem:
unreferenced object 0xffff93d1d8cc02e8 (size 248): comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s) hex dump (first 32 bytes): 00 40 85 19 d4 93 ff ff 00 10 00 00 00 00 00 00 .@.............. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: seq_open+0x2a/0x80 full_proxy_open+0x167/0x1e0 do_dentry_open+0x1e1/0x3a0 path_openat+0x961/0xa20 do_filp_open+0xae/0x120 do_sys_openat2+0x216/0x2f0 do_sys_open+0x57/0x80 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 unreferenced object 0xffff93d419854000 (size 4096): comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s) hex dump (first 32 bytes): 6b 66 65 6e 63 65 2d 23 32 35 30 3a 20 30 78 30 kfence-#250: 0x0 30 30 30 30 30 30 30 37 35 34 62 64 61 31 32 2d 0000000754bda12- backtrace: seq_read_iter+0x313/0x440 seq_read+0x14b/0x1a0 full_proxy_read+0x56/0x80 vfs_read+0xa5/0x1b0 ksys_read+0xa0/0xf0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9
I find that we can easily reproduce this problem with the following commands:
cat /sys/kernel/debug/kfence/objects echo scan > /sys/kernel/debug/kmemleak cat /sys/kernel/debug/kmemleak
The leaked memory is allocated in the stack below:
do_syscall_64 do_sys_open do_dentry_open full_proxy_open seq_open ---> alloc seq_file vfs_read full_proxy_read seq_read seq_read_iter traverse ---> alloc seq_buf
And it should have been released in the following process:
do_syscall_64 syscall_exit_to_user_mode exit_to_user_mode_prepare task_work_run ____fput __fput full_proxy_release ---> free here
However, the release function corresponding to file_operations is not implemented in kfence. As a result, a memory leak occurs. Therefore, the solution to this problem is to implement the corresponding release function.
Link: https://lkml.kernel.org/r/20211206133628.2822545-1-libaokun1@huawei.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Baokun Li libaokun1@huawei.com Reported-by: Hulk Robot hulkci@huawei.com Acked-by: Marco Elver elver@google.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Yu Kuai yukuai3@huawei.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/kfence/core.c | 1 + 1 file changed, 1 insertion(+)
--- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -578,6 +578,7 @@ static const struct file_operations obje .open = open_objects, .read = seq_read, .llseek = seq_lseek, + .release = seq_release, };
static int __init kfence_debugfs_init(void)