mirror of
https://github.com/torvalds/linux.git
synced 2026-09-25 21:21:09 -04:00
Steven Rostedt (Google)
1a6edfc7be
commit44365329f8upstream. The callback function that is used to create inodes and dentries is not protected by anything and the data that is passed to it could become stale. After eventfs_remove_dir() is called by the tracing system, it is free to remove the events that are associated to that directory. Unfortunately, that means the callbacks must not be called after that. CPU0 CPU1 ---- ---- eventfs_root_lookup() { eventfs_remove_dir() { mutex_lock(&event_mutex); ei->is_freed = set; mutex_unlock(&event_mutex); } kfree(event_call); for (...) { entry = &ei->entries[i]; r = entry->callback() { call = data; // call == event_call above if (call->flags ...) [ USE AFTER FREE BUG ] The safest way to protect this is to wrap the callback with: mutex_lock(&eventfs_mutex); if (!ei->is_freed) r = entry->callback(); else r = -1; mutex_unlock(&eventfs_mutex); This will make sure that the callback will not be called after it is freed. But now it needs to be known that the callback is called while holding internal eventfs locks, and that it must not call back into the eventfs / tracefs system. There's no reason it should anyway, but document that as well. Link: https://lore.kernel.org/all/CA+G9fYu9GOEbD=rR5eMR-=HJ8H6rMsbzDC2ZY5=Y50WpWAE7_Q@mail.gmail.com/ Link: https://lkml.kernel.org/r/[email protected] Cc: Ajay Kaher <[email protected]> Cc: Mark Rutland <[email protected]> Cc: Andrew Morton <[email protected]> Fixes:5790b1fb3d("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: Linux Kernel Functional Testing <[email protected]> Reported-by: Naresh Kamboju <[email protected]> Tested-by: Linux Kernel Functional Testing <[email protected]> Tested-by: Naresh Kamboju <[email protected]> Reviewed-by: Masami Hiramatsu (Google) <[email protected]> Signed-off-by: Steven Rostedt (Google) <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
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 Restructured Text 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.