Messages in this thread | | | Date | Wed, 4 Nov 2009 11:51:49 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: add missing free_memtype if get_vm_area_caller failed |
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* Xiaotian Feng <dfeng@redhat.com> wrote:
> When __ioremap_caller goes into get_vm_area, kernel already reserved > memtype. so if get_vm_area fails, we need to free it before return. > > Signed-off-by: Xiaotian Feng <dfeng@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: H. Peter Anvin <hpa@zytor.com> > Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> > Cc: Suresh Siddha <suresh.b.siddha@intel.com> > --- > arch/x86/mm/ioremap.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c > index 334e63c..7859f77 100644 > --- a/arch/x86/mm/ioremap.c > +++ b/arch/x86/mm/ioremap.c > @@ -196,8 +196,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr, > * Ok, go for it.. > */ > area = get_vm_area_caller(size, VM_IOREMAP, caller); > - if (!area) > + if (!area) { > + free_memtype(phys_addr, phys_addr + size); > return NULL; > + } > area->phys_addr = phys_addr; > vaddr = (unsigned long) area->addr;
Nice one!
Mind structuring this fix in a bit different way please?
The main cause of this bug is the following unclean resource-teardown pattern in __ioremap_caller():
area = get_vm_area_caller(size, VM_IOREMAP, caller); if (!area) return NULL; area->phys_addr = phys_addr; vaddr = (unsigned long) area->addr;
if (kernel_map_sync_memtype(phys_addr, size, prot_val)) { free_memtype(phys_addr, phys_addr + size); free_vm_area(area); return NULL; }
if (ioremap_page_range(vaddr, vaddr + size, phys_addr, prot)) { free_memtype(phys_addr, phys_addr + size); free_vm_area(area); return NULL; }
see how repetitive it is, and how the return sequence is duplicated?
The way we do this is to add an error path to the tail of the function:
err_free_area: free_vm_area(area); err_free_memtype: free_memtype(phys_addr, phys_addr + size); return NULL;
and changing the failure branches to:
if (!area) goto err_free_memtype; ...
if (ioremap_page_range(vaddr, vaddr + size, phys_addr, prot)) goto err_free_area;
etc.
Ok? Ingo
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