[Barrelfish-users] [New release] free() error
kornilios.kourtis at inf.ethz.ch
Sat Mar 30 16:33:40 CET 2013
On Wed, Mar 27, 2013 at 08:10:22PM +0000, Georgios Varisteas wrote:
> Using code that run before updating, I now get a page fault while
> freeing memory. The same code runs correctly on linux and I get no
> messages from valgrind neither. Thus it should be something internal.
> kernel 20: user page fault in 'pond20': addr 0 IP 4d3c8d SP a80062b1120 error 0x6
> Although I attached the disassembled portion below, I assume the error
> is at ./lib/barrelfish/slot_alloc/single_slot_alloc.c:117.
> Actually this is the last of a series of 3 calls to free() and since
> allocations were also done consecutively the addresses are consecutive.
> I can spend time to fix this myself but I'd like some pointers.
> 00000000004d3b10 <sfree>:
> 4d3c84: e8 27 64 f9 ff callq 46a0b0 <slab_alloc>
> 4d3c89: 49 89 46 08 mov %rax,0x8(%r14)
> ->4d3c8d: 44 89 28 mov %r13d,(%rax)
Not sure how much this will help, but the problem seems to be that
slab_alloc() returns NULL, which is not checked in sfree(), causing a
segfault when trying to dereference the returned pointer.
slab_alloc() returns NULL if:
a) no refill function (->refill_func) exists, or
b) calling ->refill_func did not result in new free blocks.
A first suggestion would be to try and see if we are dealing with a) or
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