4.19-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit f0c928d878e7d01b613c9ae5c971a6b1e473a938 ]
Alexei reported use after frees in inet_diag_dump_icsk() [1]
Because we use refcount_set() when various sockets are setup and inserted into ehash, we also need to make sure inet_diag_dump_icsk() wont race with the refcount_set() operations.
Jonathan Lemon sent a patch changing net_twsk_hashdance() but other spots would need risky changes.
Instead, fix inet_diag_dump_icsk() as this bug came with linux-4.10 only.
[1] Quoting Alexei :
First something iterating over sockets finds already freed tw socket:
refcount_t: increment on 0; use-after-free. WARNING: CPU: 2 PID: 2738 at lib/refcount.c:153 refcount_inc+0x26/0x30 RIP: 0010:refcount_inc+0x26/0x30 RSP: 0018:ffffc90004c8fbc0 EFLAGS: 00010282 RAX: 000000000000002b RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88085ee9d680 RSI: ffff88085ee954c8 RDI: ffff88085ee954c8 RBP: ffff88010ecbd2c0 R08: 0000000000000000 R09: 000000000000174c R10: ffffffff81e7c5a0 R11: 0000000000000000 R12: 0000000000000000 R13: ffff8806ba9bf210 R14: ffffffff82304600 R15: ffff88010ecbd328 FS: 00007f81f5a7d700(0000) GS:ffff88085ee80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f81e2a95000 CR3: 000000069b2eb006 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: inet_diag_dump_icsk+0x2b3/0x4e0 [inet_diag] // sock_hold(sk); in net/ipv4/inet_diag.c:1002 ? kmalloc_large_node+0x37/0x70 ? __kmalloc_node_track_caller+0x1cb/0x260 ? __alloc_skb+0x72/0x1b0 ? __kmalloc_reserve.isra.40+0x2e/0x80 __inet_diag_dump+0x3b/0x80 [inet_diag] netlink_dump+0x116/0x2a0 netlink_recvmsg+0x205/0x3c0 sock_read_iter+0x89/0xd0 __vfs_read+0xf7/0x140 vfs_read+0x8a/0x140 SyS_read+0x3f/0xa0 do_syscall_64+0x5a/0x100
then a minute later twsk timer fires and hits two bad refcnts for this freed socket:
refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 31 PID: 0 at lib/refcount.c:228 refcount_dec+0x2e/0x40 Modules linked in: RIP: 0010:refcount_dec+0x2e/0x40 RSP: 0018:ffff88085f5c3ea8 EFLAGS: 00010296 RAX: 000000000000002c RBX: ffff88010ecbd2c0 RCX: 000000000000083f RDX: 0000000000000000 RSI: 00000000000000f6 RDI: 000000000000003f RBP: ffffc90003c77280 R08: 0000000000000000 R09: 00000000000017d3 R10: ffffffff81e7c5a0 R11: 0000000000000000 R12: ffffffff82ad2d80 R13: ffffffff8182de00 R14: ffff88085f5c3ef8 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88085f5c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fbe42685250 CR3: 0000000002209001 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> inet_twsk_kill+0x9d/0xc0 // inet_twsk_bind_unhash(tw, hashinfo); call_timer_fn+0x29/0x110 run_timer_softirq+0x36b/0x3a0
refcount_t: underflow; use-after-free. WARNING: CPU: 31 PID: 0 at lib/refcount.c:187 refcount_sub_and_test+0x46/0x50 RIP: 0010:refcount_sub_and_test+0x46/0x50 RSP: 0018:ffff88085f5c3eb8 EFLAGS: 00010296 RAX: 0000000000000026 RBX: ffff88010ecbd2c0 RCX: 000000000000083f RDX: 0000000000000000 RSI: 00000000000000f6 RDI: 000000000000003f RBP: ffff88010ecbd358 R08: 0000000000000000 R09: 000000000000185b R10: ffffffff81e7c5a0 R11: 0000000000000000 R12: ffff88010ecbd358 R13: ffffffff8182de00 R14: ffff88085f5c3ef8 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88085f5c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fbe42685250 CR3: 0000000002209001 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> inet_twsk_put+0x12/0x20 // inet_twsk_put(tw); call_timer_fn+0x29/0x110 run_timer_softirq+0x36b/0x3a0
Fixes: 67db3e4bfbc9 ("tcp: no longer hold ehash lock while calling tcp_get_info()") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: Alexei Starovoitov ast@kernel.org Cc: Jonathan Lemon jonathan.lemon@gmail.com Acked-by: Jonathan Lemon jonathan.lemon@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/inet_diag.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/ipv4/inet_diag.c +++ b/net/ipv4/inet_diag.c @@ -998,7 +998,9 @@ next_chunk: if (!inet_diag_bc_sk(bc, sk)) goto next_normal;
- sock_hold(sk); + if (!refcount_inc_not_zero(&sk->sk_refcnt)) + goto next_normal; + num_arr[accum] = num; sk_arr[accum] = sk; if (++accum == SKARR_SZ)