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0b2d71a7c8
After running the program 'ioctl_pidfd03' of Linux Test Project (LTP) or
the program 'pidfd_info_test' in 'tools/testing/selftests/pidfd' of the
kernel source, kmemleak reports the following memory leaks:
# cat /sys/kernel/debug/kmemleak
unreferenced object 0xff110020e5988000 (size 8216):
comm "ioctl_pidfd03", pid 10853, jiffies 4294800031
hex dump (first 32 bytes):
02 40 00 00 00 00 00 00 10 00 00 00 00 00 00 00 .@..............
00 00 00 00 af 01 00 00 80 00 00 00 00 00 00 00 ................
backtrace (crc 69483047):
kmem_cache_alloc_node_noprof+0x2fb/0x410
copy_process+0x178/0x1740
kernel_clone+0x99/0x3b0
__do_sys_clone3+0xbe/0x100
do_syscall_64+0x7b/0x2c0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
...
unreferenced object 0xff11002097b70000 (size 8216):
comm "pidfd_info_test", pid 11840, jiffies 4294889165
hex dump (first 32 bytes):
06 40 00 00 00 00 00 00 10 00 00 00 00 00 00 00 .@..............
00 00 00 00 b5 00 00 00 80 00 00 00 00 00 00 00 ................
backtrace (crc a6286bb7):
kmem_cache_alloc_node_noprof+0x2fb/0x410
copy_process+0x178/0x1740
kernel_clone+0x99/0x3b0
__do_sys_clone3+0xbe/0x100
do_syscall_64+0x7b/0x2c0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
...
The leak occurs because pidfd_info() obtains a task_struct via
get_pid_task() but never calls put_task_struct() to drop the reference,
leaving task->usage unbalanced.
Fix the issue by adding '__free(put_task) = NULL' to the local variable
'task', ensuring that put_task_struct() is automatically invoked when
the variable goes out of scope.
Fixes: 7477d7dce4 ("pidfs: allow to retrieve exit information")
Signed-off-by: Adrian Huang (Lenovo) <adrianhuang0701@gmail.com>
Link: https://lore.kernel.org/20250814094453.15232-1-adrianhuang0701@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.