dbfcef6b0f
Below is the synchronization issue between unmount and kjournald2 contexts, which results into use after free issue in kjournald2(). Fix this issue by using journal->j_state_lock to synchronize the wait_event() done in journal_kill_thread() and the wake_up() done in kjournald2(). TASK 1: umount cmd: |--jbd2_journal_destroy() { |--journal_kill_thread() { write_lock(&journal->j_state_lock); journal->j_flags |= JBD2_UNMOUNT; ... write_unlock(&journal->j_state_lock); wake_up(&journal->j_wait_commit); TASK 2 wakes up here: kjournald2() { ... checks JBD2_UNMOUNT flag and calls goto end-loop; ... end_loop: write_unlock(&journal->j_state_lock); journal->j_task = NULL; --> If this thread gets pre-empted here, then TASK 1 wait_event will exit even before this thread is completely done. wait_event(journal->j_wait_done_commit, journal->j_task == NULL); ... write_lock(&journal->j_state_lock); write_unlock(&journal->j_state_lock); } |--kfree(journal); } } wake_up(&journal->j_wait_done_commit); --> this step now results into use after free issue. } Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
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Documentation | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.