diff options
Diffstat (limited to 'src/libstore/lock.cc')
| -rw-r--r-- | src/libstore/lock.cc | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/src/libstore/lock.cc b/src/libstore/lock.cc index f1356fdca..fa718f55d 100644 --- a/src/libstore/lock.cc +++ b/src/libstore/lock.cc @@ -67,13 +67,26 @@ bool UserLock::findFreeUser() { #if __linux__ /* Get the list of supplementary groups of this build user. This is usually either empty or contains a group such as "kvm". */ - supplementaryGIDs.resize(10); - int ngroups = supplementaryGIDs.size(); - int err = getgrouplist(pw->pw_name, pw->pw_gid, - supplementaryGIDs.data(), &ngroups); + int ngroups = 32; // arbitrary initial guess + supplementaryGIDs.resize(ngroups); + + int err = getgrouplist(pw->pw_name, pw->pw_gid, supplementaryGIDs.data(), + &ngroups); + + // Our initial size of 32 wasn't sufficient, the correct size has + // been stored in ngroups, so we try again. + if (err == -1) { + supplementaryGIDs.resize(ngroups); + err = getgrouplist(pw->pw_name, pw->pw_gid, supplementaryGIDs.data(), + &ngroups); + } + + // If it failed once more, then something must be broken. if (err == -1) - throw Error("failed to get list of supplementary groups for '%1%'", pw->pw_name); + throw Error("failed to get list of supplementary groups for '%1%'", + pw->pw_name); + // Finally, trim back the GID list to its real size supplementaryGIDs.resize(ngroups); #endif |