Phil reports that adding elements, flushing and re-adding them
right away:
nft add table t '{ set s { type ipv4_addr . inet_service; flags interval; }; }'
nft add element t s '{ 10.0.0.1 . 22-25, 10.0.0.1 . 10-20 }'
nft flush set t s
nft add element t s '{ 10.0.0.1 . 10-20, 10.0.0.1 . 22-25 }'
triggers, almost reliably, a crash like this one:
[ 71.319848] general protection fault, probably for non-canonical address 0x6f6b6e696c2e756e: 0000 [#1] PREEMPT SMP PTI
[ 71.321540] CPU: 3 PID: 1201 Comm: kworker/3:2 Not tainted 5.6.0-rc1-00377-g2bb07f4e1d861 #192
[ 71.322746] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190711_202441-buildvm-armv7-10.arm.fedoraproject.org-2.fc31 04/01/2014
[ 71.324430] Workqueue: events nf_tables_trans_destroy_work [nf_tables]
[ 71.325387] RIP: 0010:nft_set_elem_destroy+0xa5/0x110 [nf_tables]
[ 71.326164] Code: 89 d4 84 c0 74 0e 8b 77 44 0f b6 f8 48 01 df e8 41 ff ff ff 45 84 e4 74 36 44 0f b6 63 08 45 84 e4 74 2c 49 01 dc 49 8b 04 24 <48> 8b 40 38 48 85 c0 74 4f 48 89 e7 4c 8b
[ 71.328423] RSP: 0018:ffffc9000226fd90 EFLAGS: 00010282
[ 71.329225] RAX: 6f6b6e696c2e756e RBX: ffff88813ab79f60 RCX: ffff88813931b5a0
[ 71.330365] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff88813ab79f9a
[ 71.331473] RBP: ffff88813ab79f60 R08: 0000000000000008 R09: 0000000000000000
[ 71.332627] R10: 000000000000021c R11: 0000000000000000 R12: ffff88813ab79fc2
[ 71.333615] R13: ffff88813b3adf50 R14: dead000000000100 R15: ffff88813931b8a0
[ 71.334596] FS: 0000000000000000(0000) GS:ffff88813bd80000(0000) knlGS:0000000000000000
[ 71.335780] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 71.336577] CR2: 000055ac683710f0 CR3: 000000013a222003 CR4: 0000000000360ee0
[ 71.337533] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 71.338557] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 71.339718] Call Trace:
[ 71.340093] nft_pipapo_destroy+0x7a/0x170 [nf_tables_set]
[ 71.340973] nft_set_destroy+0x20/0x50 [nf_tables]
[ 71.341879] nf_tables_trans_destroy_work+0x246/0x260 [nf_tables]
[ 71.342916] process_one_work+0x1d5/0x3c0
[ 71.343601] worker_thread+0x4a/0x3c0
[ 71.344229] kthread+0xfb/0x130
[ 71.344780] ? process_one_work+0x3c0/0x3c0
[ 71.345477] ? kthread_park+0x90/0x90
[ 71.346129] ret_from_fork+0x35/0x40
[ 71.346748] Modules linked in: nf_tables_set nf_tables nfnetlink 8021q [last unloaded: nfnetlink]
[ 71.348153] ---[ end trace 2eaa8149ca759bcc ]---
[ 71.349066] RIP: 0010:nft_set_elem_destroy+0xa5/0x110 [nf_tables]
[ 71.350016] Code: 89 d4 84 c0 74 0e 8b 77 44 0f b6 f8 48 01 df e8 41 ff ff ff 45 84 e4 74 36 44 0f b6 63 08 45 84 e4 74 2c 49 01 dc 49 8b 04 24 <48> 8b 40 38 48 85 c0 74 4f 48 89 e7 4c 8b
[ 71.350017] RSP: 0018:ffffc9000226fd90 EFLAGS: 00010282
[ 71.350019] RAX: 6f6b6e696c2e756e RBX: ffff88813ab79f60 RCX: ffff88813931b5a0
[ 71.350019] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff88813ab79f9a
[ 71.350020] RBP: ffff88813ab79f60 R08: 0000000000000008 R09: 0000000000000000
[ 71.350021] R10: 000000000000021c R11: 0000000000000000 R12: ffff88813ab79fc2
[ 71.350022] R13: ffff88813b3adf50 R14: dead000000000100 R15: ffff88813931b8a0
[ 71.350025] FS: 0000000000000000(0000) GS:ffff88813bd80000(0000) knlGS:0000000000000000
[ 71.350026] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 71.350027] CR2: 000055ac683710f0 CR3: 000000013a222003 CR4: 0000000000360ee0
[ 71.350028] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 71.350028] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 71.350030] Kernel panic - not syncing: Fatal exception
[ 71.350412] Kernel Offset: disabled
[ 71.365922] ---[ end Kernel panic - not syncing: Fatal exception ]---
which is caused by dangling elements that have been deactivated, but
never removed.
On a flush operation, nft_pipapo_walk() walks through all the elements
in the mapping table, which are then deactivated by nft_flush_set(),
one by one, and added to the commit list for removal. Element data is
then freed.
On transaction commit, nft_pipapo_remove() is called, and failed to
remove these elements, leading to the stale references in the mapping.
The first symptom of this, revealed by KASan, is a one-byte
use-after-free in subsequent calls to nft_pipapo_walk(), which is
usually not enough to trigger a panic. When stale elements are used
more heavily, though, such as double-free via nft_pipapo_destroy()
as in Phil's case, the problem becomes more noticeable.
The issue comes from that fact that, on a flush operation,
nft_pipapo_remove() won't get the actual key data via elem->key,
elements to be deleted upon commit won't be found by the lookup via
pipapo_get(), and removal will be skipped. Key data should be fetched
via nft_set_ext_key(), instead.
Reported-by: Phil Sutter <phil@nwl.cc>
Fixes: 3c4287f620 ("nf_tables: Add set type for arbitrary concatenation of ranges")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
212d58c106