On Fri, May 15, 2026 at 12:37:17AM +0000, Pasha Tatashin wrote: > This series addresses several issues related to the synchronization > between the reboot process and LUO session management. > > Changes in v3: > - Refined the session mutation blocking to use a dedicated global > rwsem (luo_session_serialize_rwsem) instead of pinning individual > mutexes. > - Fixed a use-after-free race in luo_file_unpreserve_files() where > a module could be released before its file handler ID was erased. > - Fixed a TOCTOU race in luo_session_retrieve() by extending the > lock scope to overlap with session mutex acquisition. > - Removed an unused 'ser' field from struct luo_session. > - Dropped the KHO skip patch as it was not needed. > > 1. Skip LUO serialization for context-preserving kexec: A > preserve_context kexec returns to the current kernel, which is unrelated > to live update where state is passed to the next kernel. Skipping > serialization avoids unnecessary work and prevents sessions from being > left in a frozen state upon return. > > 2. Block session mutations during reboot: During the reboot() syscall, > user processes may still be running concurrently and attempting to > mutate sessions. To prevent this, we introduce luo_session_serialize_rwsem. > All mutation operations (create, retrieve, release, ioctl) hold the > read lock. The serialization process holds the write lock indefinitely > on success, effectively freezing the subsystem. > > 3. Fix use-after-free in luo_file_unpreserve_files(): Reorder module_put() > to ensure the file handler module remains pinned while its operations > are being accessed during cleanup. > > 4. Fix TOCTOU race in luo_session_retrieve(): Extend the rwsem lock > scope to prevent a session from being released between lookup and > mutex acquisition. > > 5. Remove unused ser field from struct luo_session: Clean up the > session structure by removing a field that was never utilized.
Sashiko is still unhappy: https://sashiko.dev/#/patchset/[email protected] Didn't verify it's actually right, but its complaints seem legit. Among other things sashiko noted a TOCTOU issue and then found it's fixed by a later patch, maybe move the TOCTOU fix earlier in the series? > Tree: git.kernel.org/pub/scm/linux/kernel/git/tatashin/linux.git Branch: > luo-reboot-sync/v3 > > Pasha Tatashin (5): > liveupdate: skip serialization for context-preserving kexec > liveupdate: block session mutations during reboot > liveupdate: fix u-a-f in luo_file_unpreserve_files() and > luo_file_finish() > liveupdate: fix TOCTOU race in luo_session_retrieve() > liveupdate: Remove unused ser field from struct luo_session > > kernel/kexec_core.c | 8 +++++--- > kernel/liveupdate/luo_file.c | 5 +++-- > kernel/liveupdate/luo_internal.h | 2 -- > kernel/liveupdate/luo_session.c | 27 ++++++++++++++++++++------- > 4 files changed, 28 insertions(+), 14 deletions(-) > > > base-commit: 7b0b68b2b95606e65594958686833e53423f58f2 > -- > 2.53.0 > -- Sincerely yours, Mike.
