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54236ab09e
sctp_transport_seq_start() does not currently clear iter->start_fail on
success, but relies on it being zero when it is allocated (by
seq_open_net()).
This can be a problem in the following sequence:
open() // allocates iter (and implicitly sets iter->start_fail = 0)
read()
- iter->start() // fails and sets iter->start_fail = 1
- iter->stop() // doesn't call sctp_transport_walk_stop() (correct)
read() again
- iter->start() // succeeds, but doesn't change iter->start_fail
- iter->stop() // doesn't call sctp_transport_walk_stop() (wrong)
We should initialize sctp_ht_iter::start_fail to zero if ->start()
succeeds, otherwise it's possible that we leave an old value of 1 there,
which will cause ->stop() to not call sctp_transport_walk_stop(), which
causes all sorts of problems like not calling rcu_read_unlock() (and
preempt_enable()), eventually leading to more warnings like this:
BUG: sleeping function called from invalid context at mm/slab.h:388
in_atomic(): 0, irqs_disabled(): 0, pid: 16551, name: trinity-c2
Preemption disabled at:[<ffffffff819bceb6>] rhashtable_walk_start+0x46/0x150
[<ffffffff81149abb>] preempt_count_add+0x1fb/0x280
[<ffffffff83295892>] _raw_spin_lock+0x12/0x40
[<ffffffff819bceb6>] rhashtable_walk_start+0x46/0x150
[<ffffffff82ec665f>] sctp_transport_walk_start+0x2f/0x60
[<ffffffff82edda1d>] sctp_transport_seq_start+0x4d/0x150
[<ffffffff81439e50>] traverse+0x170/0x850
[<ffffffff8143aeec>] seq_read+0x7cc/0x1180
[<ffffffff814f996c>] proc_reg_read+0xbc/0x180
[<ffffffff813d0384>] do_loop_readv_writev+0x134/0x210
[<ffffffff813d2a95>] do_readv_writev+0x565/0x660
[<ffffffff813d6857>] vfs_readv+0x67/0xa0
[<ffffffff813d6c16>] do_preadv+0x126/0x170
[<ffffffff813d710c>] SyS_preadv+0xc/0x10
[<ffffffff8100334c>] do_syscall_64+0x19c/0x410
[<ffffffff83296225>] return_from_SYSCALL_64+0x0/0x6a
[<ffffffffffffffff>] 0xffffffffffffffff
Notice that this is a subtly different stacktrace from the one in commit
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|---|---|---|
| .. | ||
| associola.c | ||
| auth.c | ||
| bind_addr.c | ||
| chunk.c | ||
| debug.c | ||
| endpointola.c | ||
| input.c | ||
| inqueue.c | ||
| ipv6.c | ||
| Kconfig | ||
| Makefile | ||
| objcnt.c | ||
| offload.c | ||
| output.c | ||
| outqueue.c | ||
| primitive.c | ||
| probe.c | ||
| proc.c | ||
| protocol.c | ||
| sctp_diag.c | ||
| sm_make_chunk.c | ||
| sm_sideeffect.c | ||
| sm_statefuns.c | ||
| sm_statetable.c | ||
| socket.c | ||
| ssnmap.c | ||
| sysctl.c | ||
| transport.c | ||
| tsnmap.c | ||
| ulpevent.c | ||
| ulpqueue.c | ||