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Message-ID: <YdS7rrVPInqjpFTu@debussy>
Date: Tue, 4 Jan 2022 15:27:10 -0600
From: Nihal Jere <nihal@...aljere.xyz>
To: musl@...ts.openwall.com
Subject: Dynamic linker segfault
Hi,
ldd from master segfaults when run on [1] and [2]. It happens on
this[3] line. It seems to happen due to the intersection of a few
factors:
1. The segment at the lowest address is read-only.
2. A segment on the the same page is read/write.
3. The read/write segment has memsz > filesz.
This results in a segfault, as it tries to memset[3] on the mmap
created here[4], which has the same protection as the segment at
the lowest address (i.e. read-only).
As far as I can see, the options are to either:
a. detect this and throw an error.
b. 'or' together the protection flags of all the segments on the page.
I'm not sure what the right behavior is, but I don't think segfaulting
is right, and I'm sure there are people here what's correct.
Best,
Nihal
[1] https://github.com/golang/go/blob/master/src/debug/elf/testdata/go-relocation-test-gcc930-ranges-no-rela-x86-64
[2] https://github.com/golang/go/blob/master/src/debug/elf/testdata/go-relocation-test-gcc930-ranges-with-rela-x86-64
[3] https://git.musl-libc.org/cgit/musl/tree/ldso/dynlink.c#n783
[4] https://git.musl-libc.org/cgit/musl/tree/ldso/dynlink.c#n742
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