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Commitf08d0c3a71("pidfd: add PIDFD_SELF* sentinels to refer to own thread/process") introduced a leak by acquiring a pid reference through get_task_pid(), which increments pid->count but never drops it with put_pid(). As a result, kmemleak reports unreferenced pid objects after running tools/testing/selftests/pidfd/pidfd_test, for example: unreferenced object 0xff1100206757a940 (size 160): comm "pidfd_test", pid 16965, jiffies 4294853028 hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 fd 57 50 04 .............WP. 5e 44 00 00 00 00 00 00 18 de 34 17 01 00 11 ff ^D........4..... backtrace (crc cd8844d4): kmem_cache_alloc_noprof+0x2f4/0x3f0 alloc_pid+0x54/0x3d0 copy_process+0xd58/0x1740 kernel_clone+0x99/0x3b0 __do_sys_clone3+0xbe/0x100 do_syscall_64+0x7b/0x2c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fix this by calling put_pid() after do_pidfd_send_signal() returns. Fixes:f08d0c3a71("pidfd: add PIDFD_SELF* sentinels to refer to own thread/process") Signed-off-by: Adrian Huang (Lenovo) <adrianhuang0701@gmail.com> Link: https://lore.kernel.org/20250818134310.12273-1-adrianhuang0701@gmail.com Tested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.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.