proper error handling for fcntl F_GETOWN on modern kernels

on old kernels, there's no way to detect errors; we must assume
negative syscall return values are pgrp ids. but if the F_GETOWN_EX
fcntl works, we can get a reliable answer.

diff --git a/arch/arm/bits/fcntl.h b/arch/arm/bits/fcntl.h
index fc65ebcc7d022374d4a78ddf44f0f32fd3ca8560..9595f9cad5e1728f7f7b9c23b05fb1b2de2491a7 100644 (file)
--- a/arch/arm/bits/fcntl.h
+++ b/arch/arm/bits/fcntl.h
@@ -31,3 +31,6 @@
 #define F_GETLK 12
 #define F_SETLK 13
 #define F_SETLKW 14
+
+#define F_SETOWN_EX 15
+#define F_GETOWN_EX 16

diff --git a/arch/i386/bits/fcntl.h b/arch/i386/bits/fcntl.h
index 7f09b95c1a9bcb212331b5150356f15dc152f831..69f3a8f55685c985dcb63e5542ca602a7873d91c 100644 (file)
--- a/arch/i386/bits/fcntl.h
+++ b/arch/i386/bits/fcntl.h
@@ -31,3 +31,6 @@
 #define F_GETLK 12
 #define F_SETLK 13
 #define F_SETLKW 14
+
+#define F_SETOWN_EX 15
+#define F_GETOWN_EX 16

diff --git a/arch/x86_64/bits/fcntl.h b/arch/x86_64/bits/fcntl.h
index 7b3002105cba9bd104523ecc1694bee4668476ac..9e07229eba07de7df97aae629484d4309d882f64 100644 (file)
--- a/arch/x86_64/bits/fcntl.h
+++ b/arch/x86_64/bits/fcntl.h
@@ -31,3 +31,6 @@
 #define F_GETLK 5
 #define F_SETLK 6
 #define F_SETLKW 7
+
+#define F_SETOWN_EX 15
+#define F_GETOWN_EX 16

diff --git a/include/fcntl.h b/include/fcntl.h
index 36fb24bc3ddaeb79e9601560b60494a871fb6bdd..fcb622a2391e6c696a452a2b5d88476554ed3874 100644 (file)
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -99,6 +99,17 @@ int posix_fallocate(int, off_t, off_t);
 int lockf(int, int, off_t);
 #endif
 
+#if defined(_GNU_SOURCE)
+#define F_OWNER_TID 0
+#define F_OWNER_PID 1
+#define F_OWNER_PGRP 2
+#define F_OWNER_GID 2
+struct f_owner_ex {
+       int type;
+       pid_t pid;
+};
+#endif
+
 #if defined(_LARGEFILE64_SOURCE) || defined(_GNU_SOURCE)
 #define open64 open
 #define openat64 openat

diff --git a/src/fcntl/fcntl.c b/src/fcntl/fcntl.c
index fa5ad32ff7ecf05e337c72ce72e5160525106d47..fb7806a3dd4848f11d9866d585c77578126b49a2 100644 (file)
--- a/src/fcntl/fcntl.c
+++ b/src/fcntl/fcntl.c
@@ -1,6 +1,8 @@
+#define _GNU_SOURCE
 #include <fcntl.h>
 #include <unistd.h>
 #include <stdarg.h>
+#include <errno.h>
 #include "syscall.h"
 #include "libc.h"
 
@@ -13,6 +15,12 @@ int fcntl(int fd, int cmd, ...)
        va_end(ap);
        if (cmd == F_SETFL) arg |= O_LARGEFILE;
        if (cmd == F_SETLKW) return syscall_cp(SYS_fcntl, fd, cmd, arg);
-       if (cmd == F_GETOWN) return __syscall(SYS_fcntl, fd, cmd, arg);
+       if (cmd == F_GETOWN) {
+               struct f_owner_ex ex;
+               int ret = __syscall(SYS_fcntl, fd, F_GETOWN_EX, &ex);
+               if (ret == -EINVAL) return __syscall(SYS_fcntl, fd, cmd, arg);
+               if (ret) return __syscall_ret(ret);
+               return ex.type == F_OWNER_PGRP ? -ex.pid : ex.pid;
+       }
        return syscall(SYS_fcntl, fd, cmd, arg);
 }