On Fri, Jul 24, 2015 at 08:34:35AM -0400, Stephen Smalley wrote: > The shm implementation internally uses shmem or hugetlbfs inodes > for shm segments. As these inodes are never directly exposed to > userspace and only accessed through the shm operations which are > already hooked by security modules, mark the inodes with the > S_PRIVATE flag so that inode security initialization and permission > checking is skipped. > > This was motivated by the following lockdep warning: > Jul 22 14:36:40 fc23 kernel: > ====================================================== > Jul 22 14:36:40 fc23 kernel: [ INFO: possible circular locking > dependency detected ] > Jul 22 14:36:40 fc23 kernel: 4.2.0-0.rc3.git0.1.fc24.x86_64+debug #1 > Tainted: G W > Jul 22 14:36:40 fc23 kernel: > ------------------------------------------------------- > Jul 22 14:36:40 fc23 kernel: httpd/1597 is trying to acquire lock: > Jul 22 14:36:40 fc23 kernel: (&ids->rwsem){+++++.}, at: > [<ffffffff81385354>] shm_close+0x34/0x130 > Jul 22 14:36:40 fc23 kernel: #012but task is already holding lock: > Jul 22 14:36:40 fc23 kernel: (&mm->mmap_sem){++++++}, at: > [<ffffffff81386bbb>] SyS_shmdt+0x4b/0x180 > Jul 22 14:36:40 fc23 kernel: #012which lock already depends on the new lock. > Jul 22 14:36:40 fc23 kernel: #012the existing dependency chain (in > reverse order) is: > Jul 22 14:36:40 fc23 kernel: #012-> #3 (&mm->mmap_sem){++++++}: > Jul 22 14:36:40 fc23 kernel: [<ffffffff81109a07>] lock_acquire+0xc7/0x270 > Jul 22 14:36:40 fc23 kernel: [<ffffffff81217baa>] __might_fault+0x7a/0xa0 > Jul 22 14:36:40 fc23 kernel: [<ffffffff81284a1e>] filldir+0x9e/0x130 > Jul 22 14:36:40 fc23 kernel: [<ffffffffa019bb08>] > xfs_dir2_block_getdents.isra.12+0x198/0x1c0 [xfs] > Jul 22 14:36:40 fc23 kernel: [<ffffffffa019c5b4>] [....] This was send via git-send-email, which means that you've mangled the line wrapping when you pasted the stack trace into the git commit message. I strongly suggest that you trim the data/kernel part of these traces as it is unneccessary information, and it makes it harder to read. i.e the trace in the commit message should look more like: ====================================================== [ INFO: possible circular locking dependency detected ] 4.2.0-0.rc3.git0.1.fc24.x86_64+debug #1 Tainted: G W ------------------------------------------------------- httpd/1597 is trying to acquire lock: (&ids->rwsem){+++++.}, at: [<ffffffff81385354>] shm_close+0x34/0x130 #012but task is already holding lock: (&mm->mmap_sem){++++++}, at: [<ffffffff81386bbb>] SyS_shmdt+0x4b/0x180 #012which lock already depends on the new lock. #012the existing dependency chain (in reverse order) is: #012-> #3 (&mm->mmap_sem){++++++}: [<ffffffff81109a07>] lock_acquire+0xc7/0x270 [<ffffffff81217baa>] __might_fault+0x7a/0xa0 [<ffffffff81284a1e>] filldir+0x9e/0x130 [<ffffffffa019bb08>] xfs_dir2_block_getdents.isra.12+0x198/0x1c0 [xfs] [<ffffffffa019c5b4>] xfs_readdir+0x1b4/0x330 [xfs] [<ffffffffa019f38b>] xfs_file_readdir+0x2b/0x30 [xfs] [<ffffffff812847e7>] iterate_dir+0x97/0x130 [<ffffffff81284d21>] SyS_getdents+0x91/0x120 [<ffffffff81871d2e>] entry_SYSCALL_64_fastpath+0x12/0x76 #012-> #2 (&xfs_dir_ilock_class){++++.+}: [<ffffffff81109a07>] lock_acquire+0xc7/0x270 [<ffffffff81101e97>] down_read_nested+0x57/0xa0 [<ffffffffa01b0e57>] xfs_ilock+0x167/0x350 [xfs] [<ffffffffa01b10b8>] xfs_ilock_attr_map_shared+0x38/0x50 [xfs] [<ffffffffa014799d>] xfs_attr_get+0xbd/0x190 [xfs] [<ffffffffa01c17ad>] xfs_xattr_get+0x3d/0x70 [xfs] [<ffffffff8129962f>] generic_getxattr+0x4f/0x70 [<ffffffff8139ba52>] inode_doinit_with_dentry+0x162/0x670 [<ffffffff8139cf69>] sb_finish_set_opts+0xd9/0x230 [<ffffffff8139d66c>] selinux_set_mnt_opts+0x35c/0x660 [<ffffffff8139ff97>] superblock_doinit+0x77/0xf0 [<ffffffff813a0020>] delayed_superblock_init+0x10/0x20 [<ffffffff81272d23>] iterate_supers+0xb3/0x110 [<ffffffff813a4e5f>] selinux_complete_init+0x2f/0x40 [<ffffffff813b47a3>] security_load_policy+0x103/0x600 [<ffffffff813a6901>] sel_write_load+0xc1/0x750 [<ffffffff8126e817>] __vfs_write+0x37/0x100 [<ffffffff8126f229>] vfs_write+0xa9/0x1a0 [<ffffffff8126ff48>] SyS_write+0x58/0xd0 [<ffffffff81871d2e>] entry_SYSCALL_64_fastpath+0x12/0x76 .... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>