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Re: [PATCH] linux-user/elfload: munmap proper address in pgd_find_hole_f

From: Vincent Fazio
Subject: Re: [PATCH] linux-user/elfload: munmap proper address in pgd_find_hole_fallback
Date: Tue, 9 Mar 2021 15:04:27 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

Pinging per Laurent.

On 2/14/21 5:32 AM, Alex Bennée wrote:

Vincent Fazio <vfazio@xes-inc.com> writes:

From: Vincent Fazio <vfazio@gmail.com>

Previously, if the build host's libc did not define MAP_FIXED_NOREPLACE
or if the running kernel didn't support that flag, it was possible for
pgd_find_hole_fallback to munmap an incorrect address which could lead to
SIGSEGV if the range happened to overlap with the mapped address of the
QEMU binary.

-1, 0) = 0x7f889d331000
   munmap(0x1000, 22261224)                = 0
   --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x84b817} ---
   ++ killed by SIGSEGV +++

Now, always munmap the address returned by mmap.

Fixes: 2667e069e7b5 ("linux-user: don't use MAP_FIXED in 
Signed-off-by: Vincent Fazio <vfazio@gmail.com>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

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