commit 4bad4a31c423faa4c5160652b57fd2e7cebfb38a
Author: Jason S. McMullan <jason.mcmullan@gmail.com>
Date:   Thu Apr 30 19:46:04 2015 -0400

    udev/net_id: Only read the first 64 bytes of PCI config space
    
    The original code used fread(), which on some libc implementions
    (ie glibc 2.17) would pre-read a full 4K (PAGE_SIZE) of the
    PCI config space, when only 64 bytes were requested.
    
    I have recently come across PCIe hardware which responds with
    Completion Timeouts when accesses above 256 bytes are attempted.
    
    This can cause server systems with GHES/AEPI support to cause
    and immediate kernel panic due to the failed PCI transaction.
    
    This change replaces the buffered fread() with an explict
    unbuffered read() of 64 bytes, which corrects this issue by
    only reading the guaranteed first 64 bytes of PCIe config space.
    
    Signed-off-by: Jason S. McMullan <jason.mcmullan@gmail.com>

diff --git a/src/udev/udev-builtin-net_id.c b/src/udev/udev-builtin-net_id.c
index 78aef20..4489205 100644
--- a/src/udev/udev-builtin-net_id.c
+++ b/src/udev/udev-builtin-net_id.c
@@ -91,6 +91,7 @@
 #include <stdlib.h>
 #include <stdarg.h>
 #include <unistd.h>
+#include <fcntl.h>
 #include <string.h>
 #include <errno.h>
 #include <net/if.h>
@@ -166,15 +167,15 @@ static int dev_pci_onboard(struct udev_device *dev, struct netnames *names) {
 
 /* read the 256 bytes PCI configuration space to check the multi-function bit */
 static bool is_pci_multifunction(struct udev_device *dev) {
-        _cleanup_fclose_ FILE *f = NULL;
+        _cleanup_close_ int fd = -1;
         const char *filename;
         uint8_t config[64];
 
         filename = strjoina(udev_device_get_syspath(dev), "/config");
-        f = fopen(filename, "re");
-        if (!f)
+        fd = open(filename, O_RDONLY | O_CLOEXEC);
+        if (fd < 0)
                 return false;
-        if (fread(&config, sizeof(config), 1, f) != 1)
+        if (read(fd, &config, sizeof(config)) != sizeof(config))
                 return false;
 
         /* bit 0-6 header type, bit 7 multi/single function device */