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Cengiz Can
23e9f32c0c
commit44f3468a0aupstream. The "trigger" debugfs file has a hand-rolled ->write handler (trigger_write()) that dereferences the per-device gpio_la_poll_priv. The file is created with debugfs_create_file_unsafe(), and the handler never takes a debugfs reference. Nothing keeps the object alive while the handler runs. priv is allocated with devm_kzalloc(). devres frees it when the platform device is unbound. debugfs_create_file_unsafe() installs no full_proxy wrapper, so debugfs_remove_recursive() in gpio_la_poll_remove() does not wait for an in-flight trigger_write(). The blob_lock taken there does not help, because trigger_write() never takes it. A write that races an unbind therefore writes into freed memory: trigger_write() gpio_la_poll_remove() priv = m->private buf = memdup_user() [may sleep] mutex_lock(&priv->blob_lock) debugfs_remove_recursive() [no wait] mutex_unlock(&priv->blob_lock) (remove returns; devres frees priv) priv->trig_data = buf <-- use-after-free write priv->trig_len = count The race is reachable by root via /sys/bus/platform/drivers/gpio-sloppy-logic-analyzer/unbind. Create "trigger" with debugfs_create_file() instead. Its full_proxy wrapper makes debugfs_remove_recursive() drain any in-flight ->write before it returns. The use-after-free is confirmed under KASAN with a minimal reproducer of the same debugfs_create_file_unsafe() plus devm_kzalloc() pattern (available on request); it produces a slab-use-after-free write in the handler. Fixes:7828b7bbbf("gpio: add sloppy logic analyzer using polling") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4.8 Signed-off-by: Cengiz Can <cengiz.can@canonical.com> Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Link: https://patch.msgid.link/20260730220258.358169-2-cengiz.can@canonical.com Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.