50 lines
2.1 KiB
Diff
50 lines
2.1 KiB
Diff
From a5aff1972c9e3981566414b09a28e331ccd2be5d Mon Sep 17 00:00:00 2001
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From: Rich Felker <dalias@aerifal.cx>
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Date: Thu, 17 Sep 2020 15:09:46 -0400
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Subject: [PATCH 237/513] avoid set*id/setrlimit misbehavior and hang in
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vforked/cloned child
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taking the deprecated/dropped vfork spec strictly, doing pretty much
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anything but execve in the child is wrong and undefined. however,
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these are commonly needed operations to setup the child state before
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exec, and historical implementations tolerated them.
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for single-threaded parents, these operations already worked as
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expected in the vforked child. however, due to the need for __synccall
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to synchronize id/resource limit changes among all threads, calling
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these functions in the vforked child of a multithreaded parent caused
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a misdirected broadcast signaling of all threads in the parent. these
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signals could kill the parent entirely if the synccall signal handler
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had never been installed in the parent, or could be ignored if it had,
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or could signal/kill one or more utterly wrong processes if the parent
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already terminated (due to vfork semantics, only possible via fatal
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signal) and the parent tids were recycled. in any case, the expected
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number of semaphore posts would never happen, so the child would
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permanently hang (with all signals blocked) waiting for them.
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to mitigate this, and also make the normal usage case work as
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intended, treat the condition where the caller's actual tid does not
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match the tid in its thread structure as single-threaded, and bypass
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the entire synccall broadcast operation.
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---
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src/thread/synccall.c | 3 ++-
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1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/src/thread/synccall.c b/src/thread/synccall.c
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index 648a6ad4..d58c851f 100644
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--- a/src/thread/synccall.c
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+++ b/src/thread/synccall.c
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@@ -63,7 +63,8 @@ void __synccall(void (*func)(void *), void *ctx)
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sem_init(&target_sem, 0, 0);
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sem_init(&caller_sem, 0, 0);
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- if (!libc.threads_minus_1) goto single_threaded;
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+ if (!libc.threads_minus_1 || __syscall(SYS_gettid) != self->tid)
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+ goto single_threaded;
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callback = func;
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context = ctx;
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--
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2.41.0
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