[Xen-devel] [PATCH 1/2] xen-pciback: simplify and tighten parsing of device IDs

["Jan Beulich" <JBeulich@xxxxxxxx>]

Now that at least one of the conformance problems of the kernel's
sscanf() was addressed (commit da99075c1d368315e1508b6143226c0d27b621e0),
we can improve the parsing done in xen-pciback both in terms of code
readability and correctness (in particular properly rejecting input
strings not well formed).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

---
 drivers/xen/xen-pciback/pci_stub.c |   83 +++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 44 deletions(-)

--- 3.7-rc3-xen-pciback.orig/drivers/xen/xen-pciback/pci_stub.c
+++ 3.7-rc3-xen-pciback/drivers/xen/xen-pciback/pci_stub.c
@@ -897,42 +897,35 @@ static struct pci_driver xen_pcibk_pci_d
 static inline int str_to_slot(const char *buf, int *domain, int *bus,
                              int *slot, int *func)
 {
-       int err;
-       char wc = '*';
+       int parsed = 0;
 
-       err = sscanf(buf, " %x:%x:%x.%x", domain, bus, slot, func);
-       switch (err) {
+       switch (sscanf(buf, " %x:%x:%x.%x %n", domain, bus, slot, func,
+                      &parsed)) {
        case 3:
                *func = -1;
-               err = sscanf(buf, " %x:%x:%x.%c", domain, bus, slot, &wc);
+               sscanf(buf, " %x:%x:%x.* %n", domain, bus, slot, &parsed);
                break;
        case 2:
                *slot = *func = -1;
-               err = sscanf(buf, " %x:%x:*.%c", domain, bus, &wc);
-               if (err >= 2)
-                       ++err;
+               sscanf(buf, " %x:%x:*.* %n", domain, bus, &parsed);
                break;
        }
-       if (err == 4 && wc == '*')
+       if (parsed && !buf[parsed])
                return 0;
-       else if (err < 0)
-               return -EINVAL;
 
        /* try again without domain */
        *domain = 0;
-       wc = '*';
-       err = sscanf(buf, " %x:%x.%x", bus, slot, func);
-       switch (err) {
+       switch (sscanf(buf, " %x:%x.%x %n", bus, slot, func, &parsed)) {
        case 2:
                *func = -1;
-               err = sscanf(buf, " %x:%x.%c", bus, slot, &wc);
+               sscanf(buf, " %x:%x.* %n", bus, slot, &parsed);
                break;
        case 1:
                *slot = *func = -1;
-               err = sscanf(buf, " %x:*.%c", bus, &wc) + 1;
+               sscanf(buf, " %x:*.* %n", bus, &parsed);
                break;
        }
-       if (err == 3 && wc == '*')
+       if (parsed && !buf[parsed])
                return 0;
 
        return -EINVAL;
@@ -941,13 +934,20 @@ static inline int str_to_slot(const char
 static inline int str_to_quirk(const char *buf, int *domain, int *bus, int
                               *slot, int *func, int *reg, int *size, int *mask)
 {
-       int err;
+       int parsed = 0;
+
+       sscanf(buf, " %4x:%2x:%2x.%d-%8x:%1x:%8x %n", domain, bus, slot, func,
+              reg, size, mask, &parsed);
+       if (parsed && !buf[parsed])
+               return 0;
 
-       err =
-           sscanf(buf, " %04x:%02x:%02x.%d-%08x:%1x:%08x", domain, bus, slot,
-                  func, reg, size, mask);
-       if (err == 7)
+       /* try again without domain */
+       *domain = 0;
+       sscanf(buf, " %2x:%2x.%d-%8x:%1x:%8x %n", bus, slot, func, reg, size,
+              mask, &parsed);
+       if (parsed && !buf[parsed])
                return 0;
+
        return -EINVAL;
 }
 
@@ -1339,8 +1339,6 @@ static int __init pcistub_init(void)
 
        if (pci_devs_to_hide && *pci_devs_to_hide) {
                do {
-                       char wc = '*';
-
                        parsed = 0;
 
                        err = sscanf(pci_devs_to_hide + pos,
@@ -1349,51 +1347,48 @@ static int __init pcistub_init(void)
                        switch (err) {
                        case 3:
                                func = -1;
-                               err = sscanf(pci_devs_to_hide + pos,
-                                            " (%x:%x:%x.%c) %n",
-                                            &domain, &bus, &slot, &wc,
-                                            &parsed);
+                               sscanf(pci_devs_to_hide + pos,
+                                      " (%x:%x:%x.*) %n",
+                                      &domain, &bus, &slot, &parsed);
                                break;
                        case 2:
                                slot = func = -1;
-                               err = sscanf(pci_devs_to_hide + pos,
-                                            " (%x:%x:*.%c) %n",
-                                            &domain, &bus, &wc, &parsed) + 1;
+                               sscanf(pci_devs_to_hide + pos,
+                                      " (%x:%x:*.*) %n",
+                                      &domain, &bus, &parsed);
                                break;
                        }
 
-                       if (err != 4 || wc != '*') {
+                       if (!parsed) {
                                domain = 0;
-                               wc = '*';
                                err = sscanf(pci_devs_to_hide + pos,
                                             " (%x:%x.%x) %n",
                                             &bus, &slot, &func, &parsed);
                                switch (err) {
                                case 2:
                                        func = -1;
-                                       err = sscanf(pci_devs_to_hide + pos,
-                                                    " (%x:%x.%c) %n",
-                                                    &bus, &slot, &wc,
-                                                    &parsed);
+                                       sscanf(pci_devs_to_hide + pos,
+                                              " (%x:%x.*) %n",
+                                              &bus, &slot, &parsed);
                                        break;
                                case 1:
                                        slot = func = -1;
-                                       err = sscanf(pci_devs_to_hide + pos,
-                                                    " (%x:*.%c) %n",
-                                                    &bus, &wc, &parsed) + 1;
+                                       sscanf(pci_devs_to_hide + pos,
+                                              " (%x:*.*) %n",
+                                              &bus, &parsed);
                                        break;
                                }
-                               if (err != 3 || wc != '*')
-                                       goto parse_error;
                        }
 
+                       if (parsed <= 0)
+                               goto parse_error;
+
                        err = pcistub_device_id_add(domain, bus, slot, func);
                        if (err)
                                goto out;
 
-                       /* if parsed<=0, we've reached the end of the string */
                        pos += parsed;
-               } while (parsed > 0 && pci_devs_to_hide[pos]);
+               } while (pci_devs_to_hide[pos]);
        }
 
        /* If we're the first PCI Device Driver to register, we're the

Attachment: linux-3.7-rc3-xen-pciback-parse.patch
Description: Text document

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