From nobody Sun Sep 4 05:10:55 2022 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4ML09C4GJNz4bStZ; Sun, 4 Sep 2022 05:10:55 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4ML09C3lBMz3lJc; Sun, 4 Sep 2022 05:10:55 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1662268255; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=CAtZQu88MSxNY/cP4DIsbDVKHY7YIOHg4Gruo1COwM4=; b=bY0ugVJne5CIvfiJEghAz+KaBiiyhAKBiscc1GMDWYPmpxs70XctQvaWoK/aGHs3eqRl1h d7Urf75kZyVsvMvUui4Aq9ru0WmxCPGR2ZA+tx8yKnJraXK0j13T0pyvPiFyDZyksk4Bla wXWIGEKrtIGm9Sr1F1lAFzjOWK6fX16G2mEfTrJHim2/Lcgr0HJmCgpToCn+UUEZUumuGX cGJRVggPz1BqZZAGAYp4CTZYjIoemXsA3xbCRNpqIum72kfnAzPYq+Q0GFOQ2h9gx7JMDC jSkl76Y5R2SFYD5k2ij1p/ysJq4KnyBCofr4+wN5W6qvUA8lh4w0Ayh1tAK8Tg== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4ML09C2nqHzNdG; Sun, 4 Sep 2022 05:10:55 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 2845Atg2082343; Sun, 4 Sep 2022 05:10:55 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 2845AtIl082342; Sun, 4 Sep 2022 05:10:55 GMT (envelope-from git) Date: Sun, 4 Sep 2022 05:10:55 GMT Message-Id: <202209040510.2845AtIl082342@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Konstantin Belousov Subject: git: a687683b997c - main - rtld: mask signals for default read locks List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-main@freebsd.org X-BeenThere: dev-commits-src-main@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: kib X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: a687683b997c5805ecd6d8278798b7ef00d9908f Auto-Submitted: auto-generated ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1662268255; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=CAtZQu88MSxNY/cP4DIsbDVKHY7YIOHg4Gruo1COwM4=; b=lioKn/7v4hXlGXcmkDyEbj/AkxBu9pIyB6q+vaO+kznUgwIkBhnLs74I79Bze56W/NbJ4B HVREezOUyNrPSsllUvlr3A5+sdad2U4SjGdxNI1C20t5gKJ/DtxEWQ+P7A3g4ylZFXbaBZ Nl60g4ieq6FuHEe70HlNjreVE/51pF3bSo+KXkwvuIMuDI3cxXjR9EE1+66nfEVaxvendW T1tb/gbkYh04Gh42EA9Wj12AyWZJiX1U+SfkotnK2yff+8E4DhnCGy8rD5EO/xx5rtxz/3 fentzzvFjQKR9fGPMV3fBFExw5y1oFVD2M+TUOcLC7Q4oqV3ncw62fKL2YxdjQ== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1662268255; a=rsa-sha256; cv=none; b=a1kyQr+W2oIdDakBRLapN0p/BfX/zjZz4maPyhDE0wa8ndbLxiUTdWSZZpdfxjZWQzDr2C pvwxWnMM425ElmsK5R36zSR/x6BxNQC8Jozp1nV5QQAimk/Xgu5ebufa8blPtCSYgfQ/3w Siz24gXYZKeyVILdVDN3u5geLuuz0ClBfnSmFZ3gwufnzhXZkCb36woWKzENrQ4k2y6h3F oKkvgPmqGh666O2VKBSSjta+36lM/sA+AKLBaqyqIwT9+56SsO8cPlICzQXbp8MPweLbYM HT55e0zAQ0dAv4cpTSKNEHsfKvL7kqjeNlKTMX/3YKpXjO3c0Pi7QkGa1Trniw== ARC-Authentication-Results: i=1; mx1.freebsd.org; none X-ThisMailContainsUnwantedMimeParts: N The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=a687683b997c5805ecd6d8278798b7ef00d9908f commit a687683b997c5805ecd6d8278798b7ef00d9908f Author: Konstantin Belousov AuthorDate: 2022-08-30 12:46:30 +0000 Commit: Konstantin Belousov CommitDate: 2022-09-04 04:28:02 +0000 rtld: mask signals for default read locks Rtld locks from libthr defer signals delivery, which means that binding is not possible while a signal handler is executed. Binding might upgrade read-locked rtld_bind_lock to write-lock, if symbol resolution requires loading filters. If a signal would be delivered while rtld is in read-locked section, and signal handler needs binding which upgrades the lock, for non-threaded image that uses default rtld locks, we get the rtld data structures modified under the top-level active rtld frame. To correct the problem, mask signals for read-locking of default locks in addition to the write-locking. It is very cheap now with sigfastblock(2). Note that the global state is used to track pre-locked state of either sigfastblock(2) or signal mask (if sigfastblock(2) is administratively disabled). It is fine for non-threaded images since there are no other threads. But I believe that it is fine for threaded images using libc_r as well, since masking signals disables preemption (I did not tested it). NetBSD PR: https://gnats.netbsd.org/56979 Reported by: tmunro Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D36396 --- libexec/rtld-elf/rtld_lock.c | 60 ++++++++++++++++++++++++++------------------ 1 file changed, 36 insertions(+), 24 deletions(-) diff --git a/libexec/rtld-elf/rtld_lock.c b/libexec/rtld-elf/rtld_lock.c index e501c03f0722..8b9a6a51e061 100644 --- a/libexec/rtld-elf/rtld_lock.c +++ b/libexec/rtld-elf/rtld_lock.c @@ -124,16 +124,6 @@ def_lock_destroy(void *lock) free(l->base); } -static void -def_rlock_acquire(void *lock) -{ - Lock *l = (Lock *)lock; - - atomic_add_acq_int(&l->lock, RC_INCR); - while (l->lock & WAFLAG) - ; /* Spin */ -} - static void sig_fastunblock(void) { @@ -145,24 +135,37 @@ sig_fastunblock(void) __sys_sigfastblock(SIGFASTBLOCK_UNBLOCK, NULL); } +static bool +def_lock_acquire_set(Lock *l, bool wlock) +{ + if (wlock) { + if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) + return (true); + } else { + atomic_add_acq_int(&l->lock, RC_INCR); + if ((l->lock & WAFLAG) == 0) + return (true); + atomic_add_int(&l->lock, -RC_INCR); + } + return (false); +} + static void -def_wlock_acquire(void *lock) +def_lock_acquire(Lock *l, bool wlock) { - Lock *l; sigset_t tmp_oldsigmask; - l = (Lock *)lock; if (ld_fast_sigblock) { for (;;) { atomic_add_32(&fsigblock, SIGFASTBLOCK_INC); - if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) + if (def_lock_acquire_set(l, wlock)) break; sig_fastunblock(); } } else { for (;;) { sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask); - if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) + if (def_lock_acquire_set(l, wlock)) break; sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL); } @@ -171,21 +174,30 @@ def_wlock_acquire(void *lock) } } +static void +def_rlock_acquire(void *lock) +{ + def_lock_acquire(lock, false); +} + +static void +def_wlock_acquire(void *lock) +{ + def_lock_acquire(lock, true); +} + static void def_lock_release(void *lock) { Lock *l; l = (Lock *)lock; - if ((l->lock & WAFLAG) == 0) - atomic_add_rel_int(&l->lock, -RC_INCR); - else { - atomic_add_rel_int(&l->lock, -WAFLAG); - if (ld_fast_sigblock) - sig_fastunblock(); - else if (atomic_fetchadd_int(&wnested, -1) == 1) - sigprocmask(SIG_SETMASK, &oldsigmask, NULL); - } + atomic_add_rel_int(&l->lock, -((l->lock & WAFLAG) == 0 ? + RC_INCR : WAFLAG)); + if (ld_fast_sigblock) + sig_fastunblock(); + else if (atomic_fetchadd_int(&wnested, -1) == 1) + sigprocmask(SIG_SETMASK, &oldsigmask, NULL); } static int