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Description of problem:
Race condition in malloc_info can result SIGSEGV.
Version-Release number of selected component (if applicable):
6.5
How reproducible:
Be unlucky enough to free enough memory that an arena is released while a different thread is doing malloc_info. Time it right and you lose.
Steps to Reproduce:
1.
2.
3.
Actual results:
SIGSEGV, core
Expected results:
accurate results back from malloc_info
Additional info:
From looking at the code, the "mi_arena" function nested inside of malloc_info calls 'mutex_unlock (&ar_ptr->mutex);' but then several lines down starts looking in arenas again. My particular core file died on line
fprintf (fp,
"<aspace type=\"total\" size=\"%zu\"/>\n"
"<aspace type=\"mprotect\" size=\"%zu\"/>\n",
heap->size, heap->mprotect_size);
The *ar_ptr looked good. But *heap was not in accessible memory. "info file" showed that the memory was no longer mapped. But 0x8000000 beyond its address still existed.
I don't grok the malloc code, but it seems that maybe the mutex shouldn't have been released yet.
I can provide details from the core if you want. I cannot provide the actual core as it contains private information.
Red Hat Enterprise Linux 6 transitioned to the Production 3 Phase on May 10, 2017. During the Production 3 Phase, Critical impact Security Advisories (RHSAs) and selected Urgent Priority Bug Fix Advisories (RHBAs) may be released as they become available.
This issue does not qualify, but we will consider incorporating an upstream change into Red Hat Enterprise Linux 7 if it becomes available.
Comment 8Red Hat Bugzilla Rules Engine
2017-11-08 09:04:11 UTC
Development Management has reviewed and declined this request. You may appeal this decision by reopening this request.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2020:0989