Neil Horman e48f129c2f [SCSI] cxgb3i: convert cdev->l2opt to use rcu to prevent NULL dereference ... This oops was reported recently: d:mon> e cpu 0xd: Vector: 300 (Data Access) at [c0000000fd4c7120] pc: d00000000076f194: .t3_l2t_get+0x44/0x524 [cxgb3] lr: d000000000b02108: .init_act_open+0x150/0x3d4 [cxgb3i] sp: c0000000fd4c73a0 msr: 8000000000009032 dar: 0 dsisr: 40000000 current = 0xc0000000fd640d40 paca = 0xc00000000054ff80 pid = 5085, comm = iscsid d:mon> t [c0000000fd4c7450] d000000000b02108 .init_act_open+0x150/0x3d4 [cxgb3i] [c0000000fd4c7500] d000000000e45378 .cxgbi_ep_connect+0x784/0x8e8 [libcxgbi] [c0000000fd4c7650] d000000000db33f0 .iscsi_if_rx+0x71c/0xb18 [scsi_transport_iscsi2] [c0000000fd4c7740] c000000000370c9c .netlink_data_ready+0x40/0xa4 [c0000000fd4c77c0] c00000000036f010 .netlink_sendskb+0x4c/0x9c [c0000000fd4c7850] c000000000370c18 .netlink_sendmsg+0x358/0x39c [c0000000fd4c7950] c00000000033be24 .sock_sendmsg+0x114/0x1b8 [c0000000fd4c7b50] c00000000033d208 .sys_sendmsg+0x218/0x2ac [c0000000fd4c7d70] c00000000033f55c .sys_socketcall+0x228/0x27c [c0000000fd4c7e30] c0000000000086a4 syscall_exit+0x0/0x40 --- Exception: c01 (System Call) at 00000080da560cfc The root cause was an EEH error, which sent us down the offload_close path in the cxgb3 driver, which in turn sets cdev->l2opt to NULL, without regard for upper layer driver (like the cxgbi drivers) which might have execution contexts in the middle of its use. The result is the oops above, when t3_l2t_get attempts to dereference L2DATA(cdev)->nentries in arp_hash right after the EEH error handler sets it to NULL. The fix is to prevent the setting of the NULL pointer until after there are no further users of it. The t3cdev->l2opt pointer is now converted to be an rcu pointer and the L2DATA macro is now called under the protection of the rcu_read_lock(). When the EEH error path: t3_adapter_error->offload_close->cxgb3_offload_deactivate Is exectured, setting of that l2opt pointer to NULL, is now gated on an rcu quiescence point, preventing, allowing L2DATA callers to safely check for a NULL pointer without concern that the underlying data will be freeded before the pointer is dereferenced. This has been tested by the reporter and shown to fix the reproted oops [nhorman: fix up unitinialised variable reported by Dan Carpenter] Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Reviewed-by: Karen Xie <kxie@chelsio.com> Cc: stable@kernel.org Signed-off-by: James Bottomley <JBottomley@Parallels.com>		2011-09-26 09:28:01 -05:00
..
core	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband	2011-07-22 14:50:12 -07:00
hw	[SCSI] cxgb3i: convert cdev->l2opt to use rcu to prevent NULL dereference	2011-09-26 09:28:01 -05:00
ulp	Merge branches 'ipoib' and 'iser' into for-next	2011-08-17 10:57:43 -07:00
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