Attachment 935884 Details for Bug 1116347 – Fix for keyrings garbage collector

[patch] Fix for keyrings garbage collector

assoc-fix-gc.patch (text/plain), 4.21 KB, created by David Howells on 2014-09-09 19:01:10 UTC

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Creator: David Howells

Created: 2014-09-09 19:01:10 UTC

Size: 4.21 KB

patch

obsolete

>commit a40a4b974bee14ba851f13b9e1cb42929e584092
>Author: David Howells <dhowells@redhat.com>
>Date:   Tue Sep 9 19:12:32 2014 +0100
>
>    KEYS: Fix termination condition in assoc array garbage collection
>    
>    It is possible for an associative array to end up with a shortcut node at the
>    root of the tree, if there are more than fan-out nodes in the tree, but they
>    all crowd into the same slot in the lowest level (ie. they all have the same
>    first nibble of their index keys).
>    
>    When assoc_array_gc() returns back up the tree after scanning some leaves, it
>    can fall off of the root and crash because it assumes that the back pointer
>    from a shortcut (after label ascend_old_tree) must point to a normal node -
>    which isn't true of a shortcut node at the root.
>    
>    Should we find we're ascending rootwards over a shortcut, we should check to
>    see if the backpointer is zero - and if it is, we have completed the scan.
>    
>    This particular bug cannot occur if the root node is not a shortcut - ie. if
>    you have fewer than 17 keys in a keyring or if you have at least two keys that
>    sit into separate slots (eg. a keyring and a non keyring).
>    
>    If we do fall off of the top of the tree, we get the following oops:
>    
>    BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
>    IP: [<ffffffff8136cea7>] assoc_array_gc+0x2f7/0x540
>    PGD dae15067 PUD cfc24067 PMD 0
>    Oops: 0000 [#1] SMP
>    Modules linked in: xt_nat xt_mark nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_rpfilter ip6t_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_ni
>    CPU: 0 PID: 26011 Comm: kworker/0:1 Not tainted 3.14.9-200.fc20.x86_64 #1
>    Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
>    Workqueue: events key_garbage_collector
>    task: ffff8800918bd580 ti: ffff8800aac14000 task.ti: ffff8800aac14000
>    RIP: 0010:[<ffffffff8136cea7>] [<ffffffff8136cea7>] assoc_array_gc+0x2f7/0x540
>    RSP: 0018:ffff8800aac15d40  EFLAGS: 00010206
>    RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8800aaecacc0
>    RDX: ffff8800daecf440 RSI: 0000000000000001 RDI: ffff8800aadc2bc0
>    RBP: ffff8800aac15da8 R08: 0000000000000001 R09: 0000000000000003
>    R10: ffffffff8136ccc7 R11: 0000000000000000 R12: 0000000000000000
>    R13: 0000000000000000 R14: 0000000000000070 R15: 0000000000000001
>    FS:  0000000000000000(0000) GS:ffff88011fc00000(0000) knlGS:0000000000000000
>    CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>    CR2: 0000000000000018 CR3: 00000000db10d000 CR4: 00000000000006f0
>    Stack:
>     ffff8800aac15d50 0000000000000011 ffff8800aac15db8 ffffffff812e2a70
>     ffff880091a00600 0000000000000000 ffff8800aadc2bc3 00000000cd42c987
>     ffff88003702df20 ffff88003702dfa0 0000000053b65c09 ffff8800aac15fd8
>    Call Trace:
>     [<ffffffff812e2a70>] ? keyring_detect_cycle_iterator+0x30/0x30
>     [<ffffffff812e3e75>] keyring_gc+0x75/0x80
>     [<ffffffff812e1424>] key_garbage_collector+0x154/0x3c0
>     [<ffffffff810a67b6>] process_one_work+0x176/0x430
>     [<ffffffff810a744b>] worker_thread+0x11b/0x3a0
>     [<ffffffff810a7330>] ? rescuer_thread+0x3b0/0x3b0
>     [<ffffffff810ae1a8>] kthread+0xd8/0xf0
>     [<ffffffff810ae0d0>] ? insert_kthread_work+0x40/0x40
>     [<ffffffff816ffb7c>] ret_from_fork+0x7c/0xb0
>     [<ffffffff810ae0d0>] ? insert_kthread_work+0x40/0x40
>    Code: 08 4c 8b 22 0f 84 bf 00 00 00 41 83 c7 01 49 83 e4 fc 41 83 ff 0f 4c 89 65 c0 0f 8f 5a fe ff ff 48 8b 45 c0 4d 63 cf 49 83 c1 02 <4e> 8b 34 c8 4d 85 f6 0f 84 be 00 00 00 41 f6 c6 01 0f 84 92
>    RIP  [<ffffffff8136cea7>] assoc_array_gc+0x2f7/0x540
>     RSP <ffff8800aac15d40>
>    CR2: 0000000000000018
>    ---[ end trace 1129028a088c0cbd ]---
>    
>    Signed-off-by: David Howells <dhowells@redhat.com>
>
>diff --git a/lib/assoc_array.c b/lib/assoc_array.c
>index ae146f0734eb..2404d03e251a 100644
>--- a/lib/assoc_array.c
>+++ b/lib/assoc_array.c
>@@ -1723,11 +1723,13 @@ ascend_old_tree:
> 		shortcut = assoc_array_ptr_to_shortcut(ptr);
> 		slot = shortcut->parent_slot;
> 		cursor = shortcut->back_pointer;
>+		if (!cursor)
>+			goto gc_complete;
> 	} else {
> 		slot = node->parent_slot;
> 		cursor = ptr;
> 	}
>-	BUG_ON(!ptr);
>+	BUG_ON(!cursor);
> 	node = assoc_array_ptr_to_node(cursor);
> 	slot++;
> 	goto continue_node;

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Attachments on bug 1116347: 935884