From nobody Sun Jun 21 11:47:58 2026 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 4gjqMf6Yx6z6jZgb for ; Sun, 21 Jun 2026 11:47:58 +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 "YR1" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4gjqMf55Pqz3W6k for ; Sun, 21 Jun 2026 11:47:58 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1782042478; 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=sVV/udRgXuYx7WkiS78C0EO/Yz7aT6GEG6pJE/Ryfw4=; b=sB1TLrkzkTt4aiUGUGMm37YOUyw+ub7gozK90IWs0E6UIxYRx5B9t9MwEpn1lVbnmEK5bK NrjVyW+h2omkvTquWD5iwThwzlESiKR5EsOg0GDGa7aOQo5DDNLUPIweZhsShHjeBUyG7C SKjOekb3mdQbFDORZ3mjf+NymTGM6ags4+Mw7PX71fzqoq/3g5JOW5+9ZpOyxUfAV7qkFs twjVlJ9zZYNp8FHzpbvfauOoFmm/SxAEiPoCVIW+I0p+x2rgPR2UIdHJdBnpGewqaQcE6+ b9sswn6xV29BmfKTW2fFcd1uP+7jiOT3f10sgKzS636fRaE4Swa4JdbClN+zow== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1782042478; a=rsa-sha256; cv=none; b=FuFuVUEPI+cEg9q6heb+GDhY8ybsX5PwiwTUKjUBjSwroQxnj8FG6VXVX0vBOlxGSx41Qv dd7YA46dHlNhRI4+3Ej4txM+x6NpX461ZhgfPh1lgOAe7zWHU5xujRBr92xUziDJr/2ilH Uqe1CrBcwaS1mTdcx5R1yVaruZhi4hj4eat/gDxn0n5xzSmrBIC0Hso6L00ccZY+EJgEeM ko5NoOviQqaVrSRwMgjr2reSD+DQ6NogDB1y7qDF7rxhjeWJlFfQY/vqxxKZN01NdxgFIB q/6pq83eaz0wP2Q4DGS7HkJsZhjG85kl+wTfjIrwW54DXO0rcs6lrheHGmuayQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1782042478; 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=sVV/udRgXuYx7WkiS78C0EO/Yz7aT6GEG6pJE/Ryfw4=; b=mEQoanHMWN9z9kaffJXmpfLCzZ174tylW77HseTsUGc5TsFw63cmyKrGawwAHAaqsYMmqF DUgVsxZnmFoXDLttYnrEWRfMSkMOmh1FtZODMzAnn+xWeCVVWqltHSRKtdyZJhBHdhJMMI 3UDTdpLEyac13eXjgkc7iksCgYTcVnOeq3ndCQ/GsrB4NvXBD06xJpeDQPbjXrRadwDMeB duHGFfCWBx7nAB8SHYuizfXh7WQidHFg6fXtGzzfFGI+gNMz3h4mPI+xNAmw67xFjZeFON 2FBWE45X8Pi3HqF7s2Xjw303Lq4Fbdhs/bEsJ5kpCrlmc59axmuyMIV/V7P9Nw== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4gjqMf3kdCz1FJK for ; Sun, 21 Jun 2026 11:47:58 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 254f5 by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Sun, 21 Jun 2026 11:47:58 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Konstantin Belousov Subject: git: e1a84b7708c2 - main - execve_block(): a mechanism for mutual exclusion with execve() on the process 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: X-BeenThere: dev-commits-src-main@freebsd.org Sender: owner-dev-commits-src-main@FreeBSD.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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: e1a84b7708c2514769625c2af6c5034694013b6a Auto-Submitted: auto-generated Date: Sun, 21 Jun 2026 11:47:58 +0000 Message-Id: <6a37cf6e.254f5.1a6b2154@gitrepo.freebsd.org> The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=e1a84b7708c2514769625c2af6c5034694013b6a commit e1a84b7708c2514769625c2af6c5034694013b6a Author: Konstantin Belousov AuthorDate: 2026-05-26 17:36:20 +0000 Commit: Konstantin Belousov CommitDate: 2026-06-21 11:46:52 +0000 execve_block(): a mechanism for mutual exclusion with execve() on the process A consumer of execve_block(9) is synchorized with the execution of execve(2) family of syscalls, ensuring that execve_block region is mutually exclusive with the execve processing. Either execve_block() or execve() would sleep until other finishes. Reviewed by: markj Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D57497 --- sys/kern/kern_exec.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++-- sys/kern/kern_exit.c | 1 + sys/kern/kern_thread.c | 4 +-- sys/sys/imgact.h | 3 +++ sys/sys/proc.h | 3 ++- 5 files changed, 75 insertions(+), 5 deletions(-) diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c index de6d8b08cec3..7c25dc60960d 100644 --- a/sys/kern/kern_exec.c +++ b/sys/kern/kern_exec.c @@ -385,6 +385,62 @@ execve_nosetid(struct image_params *imgp) } } +/* + * Returns true if the execblock was obtained, in this case the + * process lock is kept. Returns false if the execblock was not + * obtained, but the function slept and the lock was dropped. + */ +bool +execve_block(struct thread *td, struct proc *p) +{ + PROC_LOCK_ASSERT(p, MA_OWNED); + MPASS(td == curthread); + MPASS(p != td->td_proc || (p->p_flag & P_INEXEC) == 0); + + if (p != td->td_proc && (p->p_flag & P_INEXEC) != 0) { + p->p_flag |= P_INEXEC_WAIT; + msleep(&p->p_execblock, &p->p_mtx, PDROP, "inexec", 0); + return (false); + } + MPASS(p->p_execblock < UINT_MAX); + p->p_execblock++; + return (true); +} + +/* + * Might drop the process lock internally, callers must re-check the + * invariants afterward. + */ +void +execve_block_wait(struct thread *td, struct proc *p) +{ + bool first; + + PROC_ASSERT_HELD(p); + PROC_LOCK_ASSERT(p, MA_OWNED); + + for (first = true;; first = false) { + if (!first) + PROC_LOCK(p); + if (execve_block(td, p)) + return; + } +} + +void +execve_unblock(struct thread *td, struct proc *p) +{ + PROC_LOCK_ASSERT(p, MA_OWNED); + MPASS(td == curthread); + + MPASS(p->p_execblock > 0); + p->p_execblock--; + if (p->p_execblock == 0 && (p->p_flag & P_INEXEC_WAIT) != 0) { + p->p_flag &= ~P_INEXEC_WAIT; + wakeup(&p->p_execblock); + } +} + /* * In-kernel implementation of execve(). All arguments are assumed to be * userspace pointers from the passed thread. @@ -440,6 +496,10 @@ do_execve(struct thread *td, struct image_args *args, struct mac *mac_p, PROC_LOCK(p); KASSERT((p->p_flag & P_INEXEC) == 0, ("%s(): process already has P_INEXEC flag", __func__)); + while (p->p_execblock != 0) { + p->p_flag |= P_INEXEC_WAIT; + msleep(&p->p_execblock, &p->p_mtx, 0, "exeblk", 0); + } p->p_flag |= P_INEXEC; PROC_UNLOCK(p); @@ -911,7 +971,10 @@ interpret: * as we're now a bona fide freshly-execed process. */ KNOTE_LOCKED(p->p_klist, NOTE_EXEC); - p->p_flag &= ~P_INEXEC; + MPASS(p->p_execblock == 0); + if ((p->p_flag & P_INEXEC_WAIT) != 0) + wakeup(&p->p_execblock); + p->p_flag &= ~(P_INEXEC | P_INEXEC_WAIT); /* clear "fork but no exec" flag, as we _are_ execing */ p->p_acflag &= ~AFORK; @@ -1007,7 +1070,9 @@ exec_fail_dealloc: exec_fail: /* we're done here, clear P_INEXEC */ PROC_LOCK(p); - p->p_flag &= ~P_INEXEC; + if ((p->p_flag & P_INEXEC_WAIT) != 0) + wakeup(&p->p_execblock); + p->p_flag &= ~(P_INEXEC | P_INEXEC_WAIT); PROC_UNLOCK(p); SDT_PROBE1(proc, , , exec__failure, error); diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c index 2f94386c9101..8f9007752b3b 100644 --- a/sys/kern/kern_exit.c +++ b/sys/kern/kern_exit.c @@ -365,6 +365,7 @@ exit1(struct thread *td, int rval, int signo) while (p->p_lock > 0) msleep(&p->p_lock, &p->p_mtx, PWAIT, "exithold", 0); + MPASS(p->p_execblock == 0); PROC_UNLOCK(p); /* Drain the limit callout while we don't have the proc locked */ callout_drain(&p->p_limco); diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c index 15a327e66c7d..28c6dcff0ceb 100644 --- a/sys/kern/kern_thread.c +++ b/sys/kern/kern_thread.c @@ -100,7 +100,7 @@ _Static_assert(offsetof(struct proc, p_pid) == 0xc4, "struct proc KBI p_pid"); _Static_assert(offsetof(struct proc, p_filemon) == 0x3c8, "struct proc KBI p_filemon"); -_Static_assert(offsetof(struct proc, p_comm) == 0x3e0, +_Static_assert(offsetof(struct proc, p_comm) == 0x3e4, "struct proc KBI p_comm"); _Static_assert(offsetof(struct proc, p_emuldata) == 0x4d0, "struct proc KBI p_emuldata"); @@ -120,7 +120,7 @@ _Static_assert(offsetof(struct proc, p_pid) == 0x78, "struct proc KBI p_pid"); _Static_assert(offsetof(struct proc, p_filemon) == 0x270, "struct proc KBI p_filemon"); -_Static_assert(offsetof(struct proc, p_comm) == 0x284, +_Static_assert(offsetof(struct proc, p_comm) == 0x288, "struct proc KBI p_comm"); _Static_assert(offsetof(struct proc, p_emuldata) == 0x318, "struct proc KBI p_emuldata"); diff --git a/sys/sys/imgact.h b/sys/sys/imgact.h index f99b1273ee02..dbb76a1d9b93 100644 --- a/sys/sys/imgact.h +++ b/sys/sys/imgact.h @@ -124,6 +124,9 @@ int exec_shell_imgact(struct image_params *); int exec_copyin_args(struct image_args *, const char *, char **, char **); int pre_execve(struct thread *td, struct vmspace **oldvmspace); void post_execve(struct thread *td, int error, struct vmspace *oldvmspace); +bool execve_block(struct thread *td, struct proc *p); +void execve_block_wait(struct thread *td, struct proc *p); +void execve_unblock(struct thread *td, struct proc *p); #endif #endif /* !_SYS_IMGACT_H_ */ diff --git a/sys/sys/proc.h b/sys/sys/proc.h index ff6e944a5ad2..20389c728f37 100644 --- a/sys/sys/proc.h +++ b/sys/sys/proc.h @@ -724,6 +724,7 @@ struct proc { int p_pendingexits; /* (c) Count of pending thread exits. */ struct filemon *p_filemon; /* (c) filemon-specific data. */ int p_pdeathsig; /* (c) Signal from parent on exit. */ + u_int p_execblock; /* (c) Blockers for execve. */ /* End area that is zeroed on creation. */ #define p_endzero p_magic @@ -852,7 +853,7 @@ struct proc { #define P_STATCHILD 0x08000000 /* Child process stopped or exited. */ #define P_INMEM 0x10000000 /* Loaded into memory, always set. */ #define P_ASYNC_EXIT 0x20000000 /* XXX */ -#define P_UNUSED2 0x40000000 /* --available-- */ +#define P_INEXEC_WAIT 0x40000000 /* Waiters for P_INEXEC/p_execblock */ #define P_PPTRACE 0x80000000 /* PT_TRACEME by vforked child. */ #define P_STOPPED (P_STOPPED_SIG|P_STOPPED_SINGLE|P_STOPPED_TRACE)