Messages in this thread | | | Date | Sun, 16 Feb 2014 00:25:08 +0100 | From | Borislav Petkov <> | Subject | Re: [BUG] unable to handle kernel NULL pointer dereference |
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On Sat, Feb 15, 2014 at 01:04:22PM -0800, John wrote: > Thanks for the reply, Boris. The .config is unmodified > from the Arch Distro default for 3.13.3-1 which can be found > here: http://pastebin.com/LPGZ8ZqA
Yep, it is that struct net *net argument to put_pipe_version() which is NULL:
12: 55 push %ebp 13: 89 e5 mov %esp,%ebp 15: 56 push %esi 16: 53 push %ebx 17: 3e 8d 74 26 00 lea %ds:0x0(%esi,%eiz,1),%esi 1c: 8b 1d 28 e9 a3 f8 mov 0xf8a3e928,%ebx 22: 89 c6 mov %eax,%esi 24: e8 59 64 5f c8 call 0xc85f6482 29: 85 db test %ebx,%ebx 2b:* 8b 86 58 08 00 00 mov 0x858(%esi),%eax <-- trapping instruction
put_pipe_version: pushl %ebp # movl %esp, %ebp #, pushl %esi # pushl %ebx # call mcount movl sunrpc_net_id, %ebx # sunrpc_net_id, sunrpc_net_id.130 movl %eax, %esi # net, net call __rcu_read_lock # testl %ebx, %ebx # sunrpc_net_id.130 movl 2136(%esi), %eax # MEM[(struct net_generic * const *)net_4(D) + 2136B], ng <-- trapping insn
[ 137.689996] ESI: 00000000 EDI: f56efc00 EBP: f568fee8 ESP: f568fee0 ^^^^^^^^
Here's the c/asm interleaved version:
static void put_pipe_version(struct net *net) { d80: 55 push %ebp d81: 89 e5 mov %esp,%ebp d83: 56 push %esi d84: 53 push %ebx d85: e8 fc ff ff ff call d86 <put_pipe_version+0x6> d86: R_386_PC32 mcount struct sunrpc_net *sn = net_generic(net, sunrpc_net_id); d8a: 8b 1d 00 00 00 00 mov 0x0,%ebx d8c: R_386_32 sunrpc_net_id spin_unlock(&pipe_version_lock); return ret; }
static void put_pipe_version(struct net *net) { d90: 89 c6 mov %eax,%esi * block, but only when acquiring spinlocks that are subject to priority * inheritance. */ static inline void rcu_read_lock(void) { __rcu_read_lock(); d92: e8 fc ff ff ff call d93 <put_pipe_version+0x13> d93: R_386_PC32 __rcu_read_lock struct net_generic *ng; void *ptr;
rcu_read_lock(); ng = rcu_dereference(net->gen); BUG_ON(id == 0 || id > ng->len); d97: 85 db test %ebx,%ebx { struct net_generic *ng; void *ptr;
rcu_read_lock(); ng = rcu_dereference(net->gen); d99: 8b 86 58 08 00 00 mov 0x858(%esi),%eax <-- trapping insn
I guess you could avoid the crash if you did
if (!net) return;
in put_pipe_version() but this hardly is the right solution. Someone else has to make sense of this thing, not me. :-)
HTH.
-- Regards/Gruss, Boris.
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