On 15-11-24 08:34, Mathew T wrote:
Hello,
I’m seeking assistance with a challenging issue involving an
executable on an ARM64 Ubuntu system. Here’s the problem and what I’ve
done to investigate it so far:
Problem Summary: I have an ARM64 executable that crashes with a
segmentation fault(early to main function, looks like when loading .so
libraries) when run independently. However, when running it with
Valgrind, the program completes its execution, although Valgrind does
report an Invalid free error.
Can you share the source? Even a cut down reproducer?
I've had a quick look at the openssl code. Maybe not the same as your
version.
void BN_clear_free(BIGNUM *a)
{
if (a == NULL)
return;
if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA))
bn_free_d(a, 1);
if (BN_get_flags(a, BN_FLG_MALLOCED)) {
OPENSSL_cleanse(a, sizeof(*a));
OPENSSL_free(a);
}
}
It looks BIGNUM has a member 'd' that actually points to the allocated
block. I also presume that at the point of failure 'a' is valid and that
its flags field is also OK.
bn_free_d is probably inlined. I don't see why we don't see the CRYPTO
function in the callstack. Maybe that's not always used?
Valgrind Output (partial):
===================
plaintext
Copy code
==2644== Invalid free() / delete / delete[] / realloc()
==2644== at 0x7127AD0: free (in
/usr/libexec/valgrind/vgpreload_memcheck-arm64-linux.so)
==2644== by 0x838C0CB: BN_clear_free (in
/usr/lib/aarch64-linux-gnu/libcrypto.so.3)
==2644== by 0x7B8CEAB: ??? (in /usr/lib/aarch64-linux-gnu/libssh.so.4.8.7)
==2644== by 0x7B9121F: ??? (in /usr/lib/aarch64-linux-gnu/libssh.so.4.8.7)
==2644== by 0x7B7DF3F: ??? (in /usr/lib/aarch64-linux-gnu/libssh.so.4.8.7)
==2644== by 0x68C5623: call_init (dl-init.c:70)
==2644== by 0x68C5623: call_init (dl-init.c:26)
==2644== by 0x68C572B: _dl_init (dl-init.c:117)
==2644== by 0x68D7CC7: ??? (in
/usr/lib/aarch64-linux-gnu/ld-linux-aarch64.so.1)
==2644== Address 0x1 is not stack'd, malloc'd or (recently) free'd
This looks like it's happening before main _dl_init. ld.so loads shared
libraries and runs any global init code (like C++ constructors).
Additional Information:
====================
The crash appears to be related to libcrypto and libssh libraries.
libssh.so.4 and libcrypto.so.3 versions on the system match the
versions the executable was compiled against.
I have attempted to gather debug symbols for these libraries to
analyze further, but only limited information is available from the
system-provided packages.
Getting debuginfo would help.
Questions:
=========
1. Could the difference in behavior (running under Valgrind vs.
standalone) indicate a specific type of issue, such as a memory
alignment problem?
The memory layout is different when running under valgrind. Mainly the
stack is in a different place. Allocation alignment is probably the same.
2. Are there recommended methods or tools, other than Valgrind and
GDB, that might help debug memory management issues specifically on
ARM64?
Sanitizers?
3. Has anyone encountered similar issues when libcrypto or libssh
functions are involved?
No, I don't use Linux arm64 much.
A+
Paul
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