Hi, There seems to be a regression in kernel 2.6.37 regarding the behavior of fcntl(F_SETLEASE) when called for the second or third time. If fcntl(F_SETOWN) or fcntl(F_SETSIG) was called before it, the second fcntl(F_SETLEASE) would undo those settings. It seems that the regression was introduced by these two commits which were fixing a leak in a file_lock struct: * 3df057ac9afe83c4af84016df3baf3a0eb1d3d33 * 8896b93f42459b18b145c69d399b62870df48061 To prevent the leak, a call to locks_free_lock() was added to free the file_lock struct that was allocated but not used because the old one was reused. The problem is that the allocated file_lock was already partially initialized with a pointer to the file descriptor and that locks_free_lock() will then call locks_release_private() which will call lease_release_private_callback() which will call f_delown() and set f_owner.signum to 0, effectively undoing the effects of fcntl(F_SETOWN) and fcntl(F_SETSIG) on that same file descriptor. I thought of a solution in the lines of having lease_init() set fl_lmops = NULL and have it set back to point to lease_manager_ops inside do_fcntl_add_lease() only after it is valid, but I didn't manage to make that work... I also thought of changing locks_free_lock() somehow to decide whether locks_release_private() should be called or not (maybe an extra __locks_free_lock() function that would not call locks_release_private() and could be inlined into locks_free_lock()?) but in the end I decided to just replace the calls to locks_free_lock(fl) with kmem_cache_free(filelock_cache, fl) directly on the places where the file_lock struct was not yet fully initialized. This issue was found on Samba and reported to their bugzilla at: https://bugzilla.samba.org/show_bug.cgi?id=8974 A more detailed description and discussion including a test case is at: https://bugzilla.kernel.org/show_bug.cgi?id=43336 Thanks, Filipe Filipe Brandenburger (1): locks: prevent side-effects of locks_release_private before file_lock is initialized fs/locks.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
