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[Bug time/21229] New: strftime race conditions related to data filled by tzset
- From: "fweimer at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Tue, 07 Mar 2017 11:19:48 +0000
- Subject: [Bug time/21229] New: strftime race conditions related to data filled by tzset
- Auto-submitted: auto-generated
https://sourceware.org/bugzilla/show_bug.cgi?id=21229
Bug ID: 21229
Summary: strftime race conditions related to data filled by
tzset
Product: glibc
Version: 2.25
Status: NEW
Severity: normal
Priority: P2
Component: time
Assignee: unassigned at sourceware dot org
Reporter: fweimer at redhat dot com
Target Milestone: ---
strftime calls tzset and then accesses __tzname and calls mktime. These
accesses do not happen under the lock which protects the global timezone
variables, so there is a data race and strftime could use unexpected timezone
data.
It is unclear if POSIX actually requires that strftime calls tzset. POSIX
says, “Local timezone information is used as though strftime() called tzset().”
If the intent is that strftime has the same side effect as calling tzset
directly, updating the tzname, daylight, timezone variables, this is a curious
way of putting it, although the same language is used for localtime.
Furthermore, with our current tzset implementation, a call to tzset means that
we have to access the file system on every call, to check if the timezone data
file hasn't changed (if such a file is used).
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