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UserLock: Fix multi-threaded access to a global variable

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Eelco Dolstra 2017-01-25 13:00:38 +01:00
parent a55f589720
commit 951357e5fb
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GPG key ID: 8170B4726D7198DE
1 changed files with 39 additions and 29 deletions
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68
src/libstore/build.cc
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@ -434,7 +434,7 @@ private:
close that file again (without closing the original file
descriptor), we lose the lock. So we have to be *very* careful
not to open a lock file on which we are holding a lock. */
static PathSet lockedPaths; /* !!! not thread-safe */
static Sync<PathSet> lockedPaths_;
Path fnUserLock;
AutoCloseFD fdUserLock;
@ -460,7 +460,7 @@ public:
};
PathSet UserLock::lockedPaths;
Sync<PathSet> UserLock::lockedPaths_;
UserLock::UserLock()
@ -499,39 +499,48 @@ UserLock::UserLock()
fnUserLock = (format("%1%/userpool/%2%") % settings.nixStateDir % pw->pw_uid).str();
if (lockedPaths.find(fnUserLock) != lockedPaths.end())
/* We already have a lock on this one. */
continue;
{
auto lockedPaths(lockedPaths_.lock());
if (lockedPaths->count(fnUserLock))
/* We already have a lock on this one. */
continue;
lockedPaths->insert(fnUserLock);
}
AutoCloseFD fd = open(fnUserLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
if (!fd)
throw SysError(format("opening user lock ‘%1%’") % fnUserLock);
try {
if (lockFile(fd.get(), ltWrite, false)) {
fdUserLock = std::move(fd);
lockedPaths.insert(fnUserLock);
user = i;
uid = pw->pw_uid;
AutoCloseFD fd = open(fnUserLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
if (!fd)
throw SysError(format("opening user lock ‘%1%’") % fnUserLock);
/* Sanity check... */
if (uid == getuid() || uid == geteuid())
throw Error(format("the Nix user should not be a member of ‘%1%’")
% settings.buildUsersGroup);
if (lockFile(fd.get(), ltWrite, false)) {
fdUserLock = std::move(fd);
user = i;
uid = pw->pw_uid;
/* Sanity check... */
if (uid == getuid() || uid == geteuid())
throw Error(format("the Nix user should not be a member of ‘%1%’")
% settings.buildUsersGroup);
#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);
if (err == -1)
throw Error(format("failed to get list of supplementary groups for ‘%1%’") % pw->pw_name);
/* 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);
if (err == -1)
throw Error(format("failed to get list of supplementary groups for ‘%1%’") % pw->pw_name);
supplementaryGIDs.resize(ngroups);
supplementaryGIDs.resize(ngroups);
#endif
return;
return;
}
} catch (...) {
lockedPaths_.lock()->erase(fnUserLock);
}
}
@ -543,8 +552,9 @@ UserLock::UserLock()
UserLock::~UserLock()
{
assert(lockedPaths.count(fnUserLock));
lockedPaths.erase(fnUserLock);
auto lockedPaths(lockedPaths_.lock());
assert(lockedPaths->count(fnUserLock));
lockedPaths->erase(fnUserLock);
}