From: David Gibson <david@gibson.dropbear.id.au>
To: dan@dancancode.com
Cc: ccan@lists.ozlabs.org
Subject: [PATCH 1/4] altstack: Increase signal stack size
Date: Tue, 16 Feb 2016 17:09:22 +1100 [thread overview]
Message-ID: <1455602965-3201-2-git-send-email-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <1455602965-3201-1-git-send-email-david@gibson.dropbear.id.au>
At present the altstack module uses a stack of size MINSIGSTKSZ for its
SIGSEGV handler. Although MINSIGSTKSZ is defined to be large enough to
execute a signal handler, it doesn't guarantee that you can do anything
very much within it.
With certain libc versions, MINSIGSTKSZ is not enough to execute the
longjmp() used in altstack. Specfically, with Ubuntu 12.04 (the default
install for Travis containers), the first time longjmp() is executed the
symbol must be resolved by the dynamic linker in a process which overruns
the MINSIGSTKSZ sized stack. That then corrupts local variables in
altstack() itself causing a number of subsequent failures.
This patch addresses the problem by changing from MINSIGSTKSZ to SIGSTKSZ
which is supposed to cover "the usual requirements for an alternate signal
stack".
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
ccan/altstack/altstack.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/ccan/altstack/altstack.c b/ccan/altstack/altstack.c
index 67f457b..640344d 100644
--- a/ccan/altstack/altstack.c
+++ b/ccan/altstack/altstack.c
@@ -92,7 +92,7 @@ int altstack(rlim_t max, void *(*fn)(void *), void *arg, void **out)
undo++;
if (setjmp(jmp) == 0) {
- unsigned char sigstk[MINSIGSTKSZ];
+ unsigned char sigstk[SIGSTKSZ];
stack_t ss = { .ss_sp = sigstk, .ss_size = sizeof(sigstk) };
struct sigaction sa = { .sa_handler = segvjmp, .sa_flags = SA_NODEFER|SA_RESETHAND|SA_ONSTACK };
--
2.5.0
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next prev parent reply other threads:[~2016-02-16 10:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-16 6:09 [PATCH 0/4] altstack: Small bugfixes David Gibson
2016-02-16 6:09 ` David Gibson [this message]
2016-02-16 6:09 ` [PATCH 2/4] altstack: Include config.h in run.c David Gibson
2016-02-16 6:09 ` [PATCH 3/4] altstack: Declare memory clobbers David Gibson
2016-02-16 17:29 ` Dan Good
2016-02-17 0:09 ` David Gibson
[not found] ` <CACNkOJPwRNWyUw+mv=RR+9hShPfUaCu3EGbNTeOhGRmmc6zA-w@mail.gmail.com>
2016-02-18 3:09 ` David Gibson
[not found] ` <CACNkOJMsLzcKVuhWwNYKw-LQJhjJT4kYCFLfbYUsYW911WVu1w@mail.gmail.com>
2016-02-18 5:49 ` David Gibson
2016-02-16 6:09 ` [PATCH 4/4] altstack: Clarify checking macros David Gibson
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