Bug 1916968
| Summary: | realpath sets errno to EINVAL on success | ||||||
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| Product: | [Fedora] Fedora | Reporter: | Jerry James <loganjerry> | ||||
| Component: | glibc | Assignee: | Carlos O'Donell <codonell> | ||||
| Status: | CLOSED NOTABUG | QA Contact: | Fedora Extras Quality Assurance <extras-qa> | ||||
| Severity: | low | Docs Contact: | |||||
| Priority: | unspecified | ||||||
| Version: | rawhide | CC: | aoliva, arjun, codonell, dj, fweimer, kdudka, law, mfabian, pfrankli, rth, sipoyare | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | x86_64 | ||||||
| OS: | Linux | ||||||
| Whiteboard: | |||||||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | 2021-01-18 21:59:39 UTC | Type: | Bug | ||||
| Regression: | --- | Mount Type: | --- | ||||
| Documentation: | --- | CRM: | |||||
| Verified Versions: | Category: | --- | |||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||
| Embargoed: | |||||||
| Attachments: |
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In general, POSIX specifies that errno only has a valid value after an unsuccessful function call. glibc follows this policy. What is the purpose of the errno check in gcl? It sounds like a bug in the code. It's part of a function that gcl uses to find a path to itself:
static int
mbin(const char *s,char *o) {
struct stat ss;
if (!stat(s,&ss) && (ss.st_mode&S_IFMT)==S_IFREG && !access(s,R_OK|X_OK)) {
massert(realpath(s,o));
return 1;
}
return 0;
}
where "massert" is a macro that sets errno to 0, evaluates its argument, then asserts that errno is still 0.
It looks like the BSD realpath() also follows the convention of returning NULL on error, so I'll talk to upstream about changing the assert. Thanks for the reply, Florian.
Interesting. On Linux, it's probably best to just read /proc/self/exe, or maybe use that directly (depending on the use case). Anyway, thanks for providing the background. I don't think this is a glibc bug, so closing. |
Created attachment 1748055 [details] Program demonstrating that realpath sets errno to EINVAL on success Description of problem: Koschei let me know today that the gcl package started failing to build. Investigation shows that this is because realpath("/proc/self/exe", buffer) returns a pointer to buffer to indicate success, but also sets errno to EINVAL. This is new behavior. The attached program, when built and run on Fedora 33 and earlier, reports: /proc/self/exe is a regular file It's real path is [path to executable] [path to executable]: Success but in Rawhide it reports: /proc/self/exe is a regular file It's real path is [path to executable] [path to executable]: Invalid argument Version-Release number of selected component (if applicable): glibc-2.32.9000-26.fc34.x86_64 How reproducible: Always Steps to Reproduce: 1. Compile the attached C program on Rawhide 2. Run it on Rawhide Actual results: See that realpath sets errno to EINVAL on success. Expected results: realpath should not touch errno or set it to zero on success Additional info: