Date: Fri, 16 Oct 2015 19:46:17 +0200 From: Salva Peiró <speiro@....upv.es> To: oss-security@...ts.openwall.com Subject: Re: CVE Request: Linux Kernel heap corruption on debug_read_tlb On 10/16/15, Florian Weimer <fweimer@...hat.com> wrote: > On 10/15/2015 03:53 PM, Greg KH wrote: >> On Thu, Oct 15, 2015 at 10:30:04AM +0200, Salva Peiró wrote: >>> Hello, >>> >>> Is there a CVE for this? If not, could one be assigned, please? >>> >>> https://patchwork.kernel.org/patch/6853351/ >>> commit e203db293863fa15b4b1917d4398fb5bd63c4e88 >>> iommu/omap: Fix debug_read_tlb() to use seq_printf() >>> >>> The debug_read_tlb() uses the sprintf() functions directly on the >>> buffer >>> allocated by buf = kmalloc(count), without taking into account the >>> size >>> of the buffer, with the consequence corrupting the heap, depending >>> on >>> the count requested by the user. >>> >>> The patch fixes the issue replacing sprintf() by seq_printf(). >> >> For a root-only-readable file? Why is a CVE needed? > > Fedora and downstreams do not system-level access to the root user by > default, as a result of the custom Secure Boot patches. This does not > matter for pure denial-of-service bugs of course, but this bug looks > like something that might allow code execution. > > Florian > The value that corrupts the SLUB allocator freelist pointer is known and predictable. In principle, it should be possible to mmap() that pointer to a user controlled page, so the SLUB allocator ends up managing a user-controlled memory memory block. -- salva
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