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SubjectRe: Kernel stack corruption with SCSI

On Fri, 3 Jan 1997, Alan Cox wrote:

> Ok I did some digging and some mmap runs. Basically in some cases an mmap
> of a page on a SCSI device does indeed cause the kernel to use more than 4K
> of kernel stack and crash. I _suspect_ its only just tripping when the
> kernel stack of the process is quite dead on a page fault during the mmap as
> its not a simple run this and crash case.
> Anyway it is a definite 2.0.x bug. I also cannot duplicate it so far with IDE

btw, does the following debugging setup in asm/processor.h make sense:


#define alloc_kernel_stack() __get_free_page(GFP_KERNEL)
#define free_kernel_stack(page) free_page((page))


#define alloc_kernel_stack() vmalloc(4096)
#define free_kernel_stack(page) vfree((page))


thus all kernel stacks are MMU protected and separated by a zero pte? I
havent checked this (yet), just wondering wether someone has done this
already. This is a bit safer (and the resulting fault is much more

-- mingo

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