Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 11 Apr 2011 10:41:44 -0700 | Subject | Re: Crash with kfree(null) on MacBook? kobject_set_name_vargs |
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2011/4/10 Rafał Miłecki <zajec5@gmail.com>: > I'm writing new axi bus driver and one of the early testers reported > it crashing for him. Andy is using MacBook and backtrace+debugging > pretty clearly point to kfree being called on null string. > > The most interesting part of code is: > axi_info("[axi_register_cores][%d] current name: %s\n", i, core->dev.kobj.name); > axi_info("[axi_register_cores][%d] calling dev_set_name with %d, %d > for 0x%03X\n", i, 0/*bus->busnumber*/, dev_id, core->id.id); > err = dev_set_name(&core->dev, "axi%d:%d", 0/*bus->busnumber*/, dev_id); > axi_info("[axi_register_cores][%d] dev_set_name result: %d\n", i, err); > > The result is: > [axi_register_cores][1] current name: (null) > [axi_register_cores][1] calling dev_set_name with 0, 0 for 0x812 > BUG: unable to handle kernel paging request at ffffeba400000000 > IP: [<ffffffff8108c4d4>] kfree+0x2a/0x8a > > Whole code: http://pastie.org/1779473 > Whole result: http://pastie.org/1779416 > > Can you help me with this issue, please? On my machine everything goes fine: > [axi_register_cores][1] current name: (null) > [axi_register_cores][1] calling dev_set_name with 0, 0 for 0x812 > [axi_register_cores][1] dev_set_name result: 0 > [axi_register_cores][1] Register dev for core 0x812 > > bcopeland on #linux-wireless suggested turning on SLAB or SLUB. Is > this going to provide some interesting info?
The disassembly of the oopsing code (kfree()) is:
0: 41 54 push %r12 2: 48 83 ff 10 cmp $0x10,%rdi 6: 55 push %rbp 7: 53 push %rbx 8: 48 89 fb mov %rdi,%rbx b: 76 78 jbe 0x85 d: 9c pushfq e: 5d pop %rbp f: fa cli 10: e8 85 21 f9 ff callq 0xfffffffffff9219a 15: 48 ba 00 00 00 00 00 movabs $0xffffea0000000000,%rdx 1c: ea ff ff 1f: 48 c1 e8 0c shr $0xc,%rax 23: 48 6b c0 38 imul $0x38,%rax,%rax 27: 48 01 d0 add %rdx,%rax 2a:* 48 8b 10 mov (%rax),%rdx <-- trapping instruction 2d: 66 85 d2 test %dx,%dx 30: 79 04 jns 0x36
and from that you can see that the parameter that was passed in to kfree (which was originally in %rdi) is now in %rbx.
That, in turn, is 0x202.
So it's not NULL. The fact that
axi_info("[axi_register_cores][%d] current name: %s\n", i, core->dev.kobj.name);
prints out NULL is because the string printout code does this:
if ((unsigned long)s < PAGE_SIZE) s = "(null)";
which admittedly is not very helpful in this case (but it's usually nicer than just oopsing).
So code->dev.kobj.name is corrupt even before.
Where that corruption comes from, I have no idea, but there is no point in blaming kfree() or dev_set_name().
Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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