On 2021/12/6 21:29, Marco Elver wrote:
On Mon, 6 Dec 2021 at 14:24, Baokun Li <libaokun1@xxxxxxxxxx> wrote: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: [<00000000db5610b3>] seq_open+0x2a/0x80 [<00000000d66ac99d>] full_proxy_open+0x167/0x1e0 [<00000000d58ef917>] do_dentry_open+0x1e1/0x3a0 [<0000000016c91867>] path_openat+0x961/0xa20 [<00000000909c9564>] do_filp_open+0xae/0x120 [<0000000059c761e6>] do_sys_openat2+0x216/0x2f0 [<00000000b7a7b239>] do_sys_open+0x57/0x80 [<00000000e559d671>] do_syscall_64+0x33/0x40 [<000000000ea1fbfd>] 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: [<000000008162c6f2>] seq_read_iter+0x313/0x440 [<0000000020b1b3e3>] seq_read+0x14b/0x1a0 [<00000000af248fbc>] full_proxy_read+0x56/0x80 [<00000000f97679d1>] vfs_read+0xa5/0x1b0 [<000000000ed8a36f>] ksys_read+0xa0/0xf0 [<00000000e559d671>] do_syscall_64+0x33/0x40 [<000000000ea1fbfd>] 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. Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
