From 14adc898a36948267bfe5c63b399996879e94c98 Mon Sep 17 00:00:00 2001

From: Andreas Gruenbacher <agruenba@redhat.com>

Date: Fri, 17 Aug 2018 14:07:31 +0200

Subject: [PATCH] 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 3013aa0bb687..721ad7f33185 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

-- 

2.19.0.rc0