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From: "nsz at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug libc/25620] Signed comparison vulnerability in the ARMv7
 memcpy() (CVE-2020-6096)
Date: Wed, 08 Apr 2020 13:34:12 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D25620

Szabolcs Nagy <nsz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nsz at gcc dot gnu.org

--- Comment #15 from Szabolcs Nagy <nsz at gcc dot gnu.org> ---
note that memmove calls memcpy with overlapping
src and dst (if dst < src).

and on an aarch64 kernel a 32bit arm executable with
mmap(0, -1U/2 + 4097, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
can succeed.

so the bug can be triggered by code using mmap and memmove correctly.

however i think relying on memcpy crashing on an overflowed
size to mitigate bugs in user code is a weak protection.
(and in general we should not guarantee that memcpy accesses
all pages in the specified range: there may be a memcpy
syscall in the future for large copies with whatever semantics
in case of ub)

--=20
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