On Sunday, December 24 2006 7:25 pm, Andrew Morton wrote: > On Mon, 25 Dec 2006 05:21:24 +0800 > > "Adam J. Richter" <[EMAIL PROTECTED]> wrote: > > Under 2.6.20-rc1 and 2.6.20-rc2, I get the following complaint > > for several network programs running on my system: > > > > [ 156.381868] BUG: sleeping function called from invalid context at > > net/core/sock.c:1523 [ 156.381876] in_atomic():1, irqs_disabled():0 > > [ 156.381881] no locks held by kio_http/9693. > > [ 156.381886] [<c01057a2>] show_trace_log_lvl+0x1a/0x2f > > [ 156.381900] [<c0105dab>] show_trace+0x12/0x14 > > [ 156.381908] [<c0105e48>] dump_stack+0x16/0x18 > > [ 156.381917] [<c011e30f>] __might_sleep+0xe5/0xeb > > [ 156.381926] [<c025942a>] lock_sock_nested+0x1d/0xc4 > > [ 156.381937] [<c01cc570>] selinux_netlbl_inode_permission+0x5a/0x8e > > [ 156.381946] [<c01c2505>] selinux_file_permission+0x96/0x9b > > [ 156.381954] [<c0175a0a>] vfs_write+0x8d/0x167 > > [ 156.381962] [<c017605a>] sys_write+0x3f/0x63 > > [ 156.381971] [<c01040c0>] syscall_call+0x7/0xb > > [ 156.381980] ======================= > > There's a glaring bug in selinux_netlbl_inode_permission() - taking > lock_sock() inside rcu_read_lock().
Sorry for the delay, I'm finally back at a machine where I can look at the code. I've been thinking about Parag Warudkar's and Ingo Molnar's patches as well as what the selinux_netlbl_inode_permission() function actually needs to do; I think the best answer isn't so much to change the socket locking calls, but to restructure the function a bit. Currently the function does the following (in order): 1. do some quick sanity checks (is the inode a socket, etc) 2. rcu_read_lock() 3. check the nlbl_state is set to NLBL_REQUIRE (otherwise return) 4. lock_sock() 5. netlabel magic 6. release_sock() 7. rcu_read_unlock() I propose changing it to the following (in order): 1. do some quick sanity checks (is the inode a socket, etc) 2. rcu_read_lock() 3. check the nlbl_state is set to NLBL_REQUIRE (otherwise return) 4. rcu_read_unlock() 5. lock_sock() 6. rcu_read_lock() 7. verify that nlbl_state is still set to NLBL_REQUIRE (otherwise return) 8. netlabel magic 9. rcu_read_unlock() 10. release_sock() This way we no longer need to worry about any special socket locking. I realize this adds a bit of duplicated work but it is my understanding that RCU lock/unlock operations are *very* fast so the extra RCU lock operations shouldn't be too bad and the extra nlbl_state check should be of minimal cost. However, I'm not the expert here, just a guy learning as he goes so any comments/feedback on the above proposal are welcome. If it turns out this approach has some merit I'll put together a patch and send it out. Once again, sorry for the regression. -- paul moore linux security @ hp - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
