From cb937740fa0dddf9c398618035054c657959c783 Mon Sep 17 00:00:00 2001
From: Andreas Gruenbacher <[email protected]>
Date: Fri, 17 Aug 2018 14:07:31 +0200
Subject: [PATCH 6/7] Switch back to syscall()

Switch back to syscall() for the *xattr system calls.  The current
mechanism of forwarding those calls to glibc breaks libraries like
libfakeroot (fakeroot) and libasan (the gcc address sanitizer; gcc
-fsanitize=address).

Those libraries provide wrappers for functions defined in other shared
libraries, usually glibc, do their own processing, and forward calls to
the original symbols looke dup via dlsym(RTLD_NEXT, "symbol_name").  In
our case, dlsym returns the libattr_*xattr wrappers.  However, when our
wrappers try calling glibc, they end up calling the libfakeroot /
libasan wrappers instead because those override the original symbols =>
recursion.

The libattr_*xattr wrappers will only be used when symbols are looked up
at runtime (dlopen / dlsym).  Programs linking against libattr will
directly use the glibc provided symbols.  Therefore, the slightly worse
performance of syscall() won't affect any of the "normal" users of
libattr.
---
 libattr/syscalls.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/libattr/syscalls.c b/libattr/syscalls.c
index 3013aa0..721ad7f 100644
--- a/libattr/syscalls.c
+++ b/libattr/syscalls.c
@@ -22,6 +22,8 @@
 
 #include "config.h"
 
+#include <unistd.h>
+#include <sys/syscall.h>
 #include <sys/xattr.h>
 
 #ifdef HAVE_VISIBILITY_ATTRIBUTE
@@ -31,67 +33,67 @@
 int libattr_setxattr(const char *path, const char *name,
 		     void *value, size_t size, int flags)
 {
-	return setxattr(path, name, value, size, flags);
+	return syscall(__NR_setxattr, path, name, value, size, flags);
 }
 
 int libattr_lsetxattr(const char *path, const char *name,
 		      void *value, size_t size, int flags)
 {
-	return lsetxattr(path, name, value, size, flags);
+	return syscall(__NR_lsetxattr, path, name, value, size, flags);
 }
 
 int libattr_fsetxattr(int filedes, const char *name,
 		      void *value, size_t size, int flags)
 {
-	return fsetxattr(filedes, name, value, size, flags);
+	return syscall(__NR_fsetxattr, filedes, name, value, size, flags);
 }
 
 ssize_t libattr_getxattr(const char *path, const char *name,
 			 void *value, size_t size)
 {
-	return getxattr(path, name, value, size);
+	return syscall(__NR_getxattr, path, name, value, size);
 }
 
 ssize_t libattr_lgetxattr(const char *path, const char *name,
 			  void *value, size_t size)
 {
-	return lgetxattr(path, name, value, size);
+	return syscall(__NR_lgetxattr, path, name, value, size);
 }
 
 ssize_t libattr_fgetxattr(int filedes, const char *name,
 			  void *value, size_t size)
 {
-	return fgetxattr(filedes, name, value, size);
+	return syscall(__NR_fgetxattr, filedes, name, value, size);
 }
 
 ssize_t libattr_listxattr(const char *path, char *list, size_t size)
 {
-	return listxattr(path, list, size);
+	return syscall(__NR_listxattr, path, list, size);
 }
 
 ssize_t libattr_llistxattr(const char *path, char *list, size_t size)
 {
-	return llistxattr(path, list, size);
+	return syscall(__NR_llistxattr, path, list, size);
 }
 
 ssize_t libattr_flistxattr(int filedes, char *list, size_t size)
 {
-	return flistxattr(filedes, list, size);
+	return syscall(__NR_flistxattr, filedes, list, size);
 }
 
 int libattr_removexattr(const char *path, const char *name)
 {
-	return removexattr(path, name);
+	return syscall(__NR_removexattr, path, name);
 }
 
 int libattr_lremovexattr(const char *path, const char *name)
 {
-	return lremovexattr(path, name);
+	return syscall(__NR_lremovexattr, path, name);
 }
 
 int libattr_fremovexattr(int filedes, const char *name)
 {
-	return fremovexattr(filedes, name);
+	return syscall(__NR_fremovexattr, filedes, name);
 }
 
 #ifdef HAVE_VISIBILITY_ATTRIBUTE
-- 
1.8.3.1