[go] syscall: don't use faccessat2 on android

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Michael Pratt (Gerrit)

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Dec 21, 2022, 12:14:39 PM12/21/22

to Michael Pratt, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Austin Clements, Changkun Ou, Gopher Robot, Brad Fitzpatrick, Ian Lance Taylor, Tobias Klauser, Kirill Kolyshkin, golang-co...@googlegroups.com

Michael Pratt submitted this change.

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  Michael Pratt: Run TryBots
  Gopher Robot: TryBots succeeded
  Austin Clements: Looks good to me, approved
  Changkun Ou: Looks good to me, but someone else must approve

syscall: don't use faccessat2 on android

The Android seccomp policy does not allow faccessat2, so attempting to
use it results in a SIGSYS. Avoid it and go straight to the fallback.

Fixes #57393.

Change-Id: I8d4e12a6f46cea5642d3b5b5a02c682529882f29
Reviewed-on: https://go-review.googlesource.com/c/go/+/458495
Reviewed-by: Austin Clements <aus...@google.com>
TryBot-Result: Gopher Robot <go...@golang.org>
Reviewed-by: Changkun Ou <ma...@changkun.de>
Run-TryBot: Michael Pratt <mpr...@google.com>
---
M src/syscall/syscall_linux.go
1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/syscall/syscall_linux.go b/src/syscall/syscall_linux.go
index 30fa641..d4cc34b 100644
--- a/src/syscall/syscall_linux.go
+++ b/src/syscall/syscall_linux.go
@@ -13,6 +13,7 @@
 
 import (
 	"internal/itoa"
+	"runtime"
 	"unsafe"
 )
 
@@ -145,8 +146,17 @@
 		return faccessat(dirfd, path, mode)
 	}
 
-	if err := faccessat2(dirfd, path, mode, flags); err != ENOSYS && err != EPERM {
-		return err
+	// Attempt to use the newer faccessat2, which supports flags directly,
+	// falling back if it doesn't exist.
+	//
+	// Don't attempt on Android, which does not allow faccessat2 through
+	// its seccomp policy [1] on any version of Android as of 2022-12-20.
+	//
+	// [1] https://cs.android.com/android/platform/superproject/+/master:bionic/libc/SECCOMP_BLOCKLIST_APP.TXT;l=4;drc=dbb8670dfdcc677f7e3b9262e93800fa14c4e417
+	if runtime.GOOS != "android" {
+		if err := faccessat2(dirfd, path, mode, flags); err != ENOSYS && err != EPERM {
+			return err
+		}
 	}
 
 	// The Linux kernel faccessat system call does not take any flags.

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