From: Guillem Jover <guillem@hadrons.org>
Date: Fri, 16 Aug 2019 00:33:46 +0000 (+0200)
Subject: [PATCH libaio 23/26] Fix io_pgetevents() syscall wrapper on 32-bit userland on 64... 
X-Git-Tag: archive/raspbian/0.3.113-10+rpi1^2~5
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=bf072ce51351d6b8187d2ed089dc908de4ba417f;p=libaio.git

[PATCH libaio 23/26] Fix io_pgetevents() syscall wrapper on 32-bit userland on 64-bit kernels

The kernel compat syscall in the kernel got introduced with a broken
layout, which requires a pointer to the actual sigset_t variable but
with the size of the running kernel, not the size of the compat code.

This means that when the wrapper sends the expected compat (32-bit)
pointer, the kernel reads a 64-bit pointer, eating with it also the
sigset size member. And then proceeds to fail the comparison of the
sigset_t size and returns EINVAL.

This really needs to be fixed in the kernel, as there's no apparent
user of the broken compat layout (from codesearch.debian.org, nor a
quick github.com search). But we have to workaround it in libaio so
that we can use kernels that have not yet been fixed.

We do that, by trying the non-broken layout (that would be used with
a 32-bit userland on a 32-bit kernel), and if that fails with -EINVAL
we retry with a structure padded to what the kernel expects.

Origin: vendor
Forwarded: not-needed
Sent-Upstream: rejected
Signed-off-by: Guillem Jover <guillem@hadrons.org>

Gbp-Pq: Name 0023-Fix-io_pgetevents-syscall-wrapper-on-32-bit-userland.patch
---

diff --git a/src/aio_pgetevents.c b/src/aio_pgetevents.c
index e12036e..89cec7b 100644
--- a/src/aio_pgetevents.c
+++ b/src/aio_pgetevents.c
@@ -45,10 +45,10 @@ int aio_pgetevents(io_context_t ctx, long min_nr, long nr,
 {
 	int ret;
 #if defined(__NR_io_pgetevents) || defined(__NR_io_pgetevents_time64)
-	struct {
-		unsigned long ss;
-		unsigned long ss_len;
-	} aio_sigset;
+	struct io_sigset aio_sigset;
+#ifndef __LP64__
+	struct io_sigset_compat aio_sigset_compat = { 0 };
+#endif
 	struct sys_timespec sys_ts;
 
 	if (aio_ring_is_empty(ctx, timeout))
@@ -76,6 +76,28 @@ int aio_pgetevents(io_context_t ctx, long min_nr, long nr,
 
 	ret = __io_pgetevents(ctx, min_nr, nr, events,
 			timeout ? &sys_ts : NULL, &aio_sigset);
+
+#ifndef __LP64__
+	/*
+	 * The compat kernel syscall got introduced with a broken layout for
+	 * its sigset argument, expecting it to contain a pointer for the
+	 * non-compat pointer size.
+	 *
+	 * To cope with this on unfixed kernels, in case we are built as a
+	 * 32-bit library (which could run on a kernel with compat code) and
+	 * when the syscall returns EINVAL due to the kernel not finding the
+	 * sigset size member when unpacking the structure, we retry with
+	 * the fixed up compat layout, which requires the padding to be
+	 * zero-filled, otherwise the 64-bit pointer will contain garbage.
+	 */
+	if (ret != -EINVAL)
+		return ret;
+
+	aio_sigset_compat.ss = (unsigned long)sigmask;
+	aio_sigset_compat.ss_len = _NSIG / 8;
+	ret = __io_pgetevents(ctx, min_nr, nr, events,
+			timeout ? &sys_ts : NULL, &aio_sigset_compat);
+#endif
 #else
 	ret = -ENOSYS;
 #endif
diff --git a/src/libaio.h b/src/libaio.h
index feeee37..e99a17b 100644
--- a/src/libaio.h
+++ b/src/libaio.h
@@ -161,6 +161,16 @@ struct io_event {
 	PADDEDul(res2, __pad4);
 };
 
+struct io_sigset {
+	unsigned long ss;
+	unsigned long ss_len;
+};
+
+struct io_sigset_compat {
+	PADDEDptr(unsigned long ss, __ss_pad);
+	unsigned long ss_len;
+};
+
 #undef PADDED
 #undef PADDEDptr
 #undef PADDEDul