coredump: shift down_write(mmap_sem) into coredump_wait() (269b005a) · Commits · 戴 / test

- move the cprm.mm_flags checks up, before we take mmap_sem - move down_write(mmap_sem) and ->core_state check from do_coredump() to coredump_wait() This simplifies the code and makes the locking symmetrical. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Roland McGrath <roland@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/exec.c

+7 −12

Original line number	Diff line number	Diff line
		@@ -1662,11 +1662,14 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
		struct task_struct *tsk = current;
		struct mm_struct *mm = tsk->mm;
		struct completion *vfork_done;
		int core_waiters;
		int core_waiters = -EBUSY;

		init_completion(&core_state->startup);
		core_state->dumper.task = tsk;
		core_state->dumper.next = NULL;

		down_write(&mm->mmap_sem);
		if (!mm->core_state)
		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
		up_write(&mm->mmap_sem);

		@@ -1860,20 +1863,12 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
		binfmt = mm->binfmt;
		if (!binfmt \|\| !binfmt->core_dump)
		goto fail;
		if (!__get_dumpable(cprm.mm_flags))
		goto fail;

		cred = prepare_creds();
		if (!cred)
		goto fail;

		down_write(&mm->mmap_sem);
		/*
		* If another thread got here first, or we are not dumpable, bail out.
		*/
		if (mm->core_state \|\| !__get_dumpable(cprm.mm_flags)) {
		up_write(&mm->mmap_sem);
		goto fail_creds;
		}

		/*
		* We cannot trust fsuid as being the "true" uid of the
		* process nor do we know its entire history. We only know it

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