uucore: correctly truncate response if getgroups shrinks #6978
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The code above this line handles the case if `res` is larger than `ngroups`, but `res < ngroups` is also a possibility, which this line attempts to address but actually does not. The original code resizes to `ngroups` which is a no-op (given that `groups` is already `ngroups` size). The correct target for re-sizing the `groups` is the result from the last `getgroups`, i.e., `res`.
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GNU testsuite comparison: |
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GNU testsuite comparison: |
sylvestre
reviewed
Dec 19, 2024
| @@ -83,13 +83,14 @@ pub fn get_groups() -> IOResult<Vec<gid_t>> { | |||
| if res == -1 { | |||
| let err = IOError::last_os_error(); | |||
| if err.raw_os_error() == Some(libc::EINVAL) { | |||
| // Number of groups changed, retry | |||
| // Number of groups has increased, retry | |||
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are you sure it is always increased ?
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POSIX.1-1988 on getgroups return value:
[EINVAL]
The gidsetsize argument is non-zero and less than the number of group IDs that would have been returned.
Since ngroups is based on earlier getgroups return value, the only case where EINVAL is returned when the indicated size (ngroups parameter for getgroups) is less than what the return list would be. If the reserved space is larger than the actual list, then res != -1.
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The code above the line with
truncatehandles the case ifresis larger thanngroups, butres < ngroupsis also a possibility, which this line attempts to address but actually does not.The original code resizes to
ngroupswhich is a no-op (given thatgroupsis alreadyngroupssize). The correct target for re-sizing thegroupsis the result from the lastgetgroups, i.e.,res.