Messages in this thread | | | From | Namhyung Kim <> | Date | Fri, 3 Feb 2017 23:49:38 +0900 | Subject | Re: [for-next][PATCH 4/8] ftrace: Reset fgd->hash in ftrace_graph_write() |
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On Fri, Feb 3, 2017 at 10:40 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org> > > fgd->hash is saved and then freed, but is never reset to either > ftrace_graph_hash nor ftrace_graph_notrace_hash. But if multiple reads are > performed, then the freed hash could be accessed again.
Argh, right. Btw did you mean multiple "write" not "read", no?
Thanks, Namhyung
> > # cd /sys/kernel/debug/tracing > # head -1000 available_filter_functions > /tmp/funcs > # cat /tmp/funcs > set_graph_function > > Causes: > > general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC > Modules linked in: [...] > CPU: 2 PID: 1337 Comm: cat Not tainted 4.10.0-rc2-test-00010-g6b052e9 #32 > Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012 > task: ffff880113a12200 task.stack: ffffc90001940000 > RIP: 0010:free_ftrace_hash+0x7c/0x160 > RSP: 0018:ffffc90001943db0 EFLAGS: 00010246 > RAX: 6b6b6b6b6b6b6b6b RBX: 6b6b6b6b6b6b6b6b RCX: 6b6b6b6b6b6b6b6b > RDX: 0000000000000002 RSI: 0000000000000001 RDI: ffff8800ce1e1d40 > RBP: ffff8800ce1e1d50 R08: 0000000000000000 R09: 0000000000006400 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: ffff8800ce1e1d40 R14: 0000000000004000 R15: 0000000000000001 > FS: 00007f9408a07740(0000) GS:ffff88011e500000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000aee1f0 CR3: 0000000116bb4000 CR4: 00000000001406e0 > Call Trace: > ? ftrace_graph_write+0x150/0x190 > ? __vfs_write+0x1f6/0x210 > ? __audit_syscall_entry+0x17f/0x200 > ? rw_verify_area+0xdb/0x210 > ? _cond_resched+0x2b/0x50 > ? __sb_start_write+0xb4/0x130 > ? vfs_write+0x1c8/0x330 > ? SyS_write+0x62/0xf0 > ? do_syscall_64+0xa3/0x1b0 > ? entry_SYSCALL64_slow_path+0x25/0x25 > Code: 01 48 85 db 0f 84 92 00 00 00 b8 01 00 00 00 d3 e0 85 c0 7e 3f 83 e8 01 48 8d 6f 10 45 31 e4 4c 8d 34 c5 08 00 00 00 49 8b 45 08 <4a> 8b 34 20 48 85 f6 74 13 48 8b 1e 48 89 ef e8 20 fa ff ff 48 > RIP: free_ftrace_hash+0x7c/0x160 RSP: ffffc90001943db0 > ---[ end trace 999b48216bf4b393 ]--- > > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > --- > kernel/trace/ftrace.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index a9cfc8713198..b7df0dcf8652 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -4858,10 +4858,13 @@ ftrace_graph_write(struct file *file, const char __user *ubuf, > if (!new_hash) > ret = -ENOMEM; > > - if (fgd->type == GRAPH_FILTER_FUNCTION) > + if (fgd->type == GRAPH_FILTER_FUNCTION) { > rcu_assign_pointer(ftrace_graph_hash, new_hash); > - else > + fgd->hash = ftrace_graph_hash; > + } else { > rcu_assign_pointer(ftrace_graph_notrace_hash, new_hash); > + fgd->hash = ftrace_graph_notrace_hash; > + } > > mutex_unlock(&graph_lock); > > -- > 2.10.2 > >
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