Bug#994969: jackd2: segfaults after today's upgrade of other Debian testing packages

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On Sun, 3 Oct 2021 at 20:47, Ryan Thoryk <ryan at thoryk.com> wrote:
>
> When I had jack dump out it's module filenames during library load, it
> only appeared to load jack_firewire once.  The clue as to what's
> happening is that valgrind reports "Bad permissions for mapped region",
> if you look at the function, it's trying to pass a string literal, the
> valgrind error means that it's trying to modify the string, and since
> it's read-only, it results in a segfault.  The string and address are valid.

"Bad permissions for mapped region at address" can also mean it tried
to read from unreadable memory. The memory was mapped at some
point in the past, so it doesn't say unallocated memory

Also consider the segfault comes from strcmp(). Why would strcmp()
ever need to write to memory? You can verify with a disassember the
segfault comes from a read

> or to create a C string and pass it to the function:

I suspect this "worked" to fix the issue only due to a memory layout
change, and luck would have it that after your rebuild it now tries to
read from readable memory (albeit still not the expected memory)