modinfo: fix module parsing with kernel >= 2.6.37

display() function returns the length of the value we are displaying + 1.
As a consequence, if we have field=value\0field=value\0field=value in the
binary, then the second occurence will be skipped as ptr will miss the first
character of the following field.

Example trying to list aliases from ixgbe.ko on a 3.2 kernel.

- In the module we have:
alias=pci:v00008086d00001560sv*sd*bc*sc*i*\0
alias=pci:v00008086d0000154Asv*sd*bc*sc*i*\0
alias=pci:v00008086d00001557sv*sd*bc*sc*i*\0
alias=pci:v00008086d0000154Fsv*sd*bc*sc*i*\0
alias=pci:v00008086d0000154Dsv*sd*bc*sc*i*\0
...

- Using modinfo -F alias ixgbe returns:
alias:          pci:v00008086d00001560sv*sd*bc*sc*i*
alias:          pci:v00008086d00001557sv*sd*bc*sc*i*
alias:          pci:v00008086d0000154Dsv*sd*bc*sc*i*
...

This problem appeared with kernel commit "modules: no need to align .modinfo
strings" b6472776816af1ed52848c93d26e3edb3b17adab in 2.6.37.

Fix this by not trusting display() return value but increment ptr by strlen(ptr)
(the same way as depmod.c does).

Signed-off-by: David Marchand <david.marchand@6wind.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/modutils/modinfo.c b/modutils/modinfo.c
index 7c978d1da..0ab942890 100644
--- a/modutils/modinfo.c
+++ b/modutils/modinfo.c
@@ -34,14 +34,14 @@ struct modinfo_env {
 	int tags;
 };
 
-static int display(const char *data, const char *pattern, int flag)
+static void display(const char *data, const char *pattern, int flag)
 {
 	if (flag) {
 		int n = printf("%s:", pattern);
 		while (n++ < 16)
 			bb_putchar(' ');
 	}
-	return printf("%s%c", data, (option_mask32 & OPT_0) ? '\0' : '\n');
+	printf("%s%c", data, (option_mask32 & OPT_0) ? '\0' : '\n');
 }
 
 static void modinfo(const char *path, const char *version,
@@ -104,7 +104,8 @@ static void modinfo(const char *path, const char *version,
 				/* field prefixes are 0x80 or 0x00 */
 				if ((ptr[-1] & 0x7F) == '\0') {
 					ptr += length + 1;
-					ptr += display(ptr, pattern, (1<<j) != tags);
+					display(ptr, pattern, (1<<j) != tags);
+					ptr += strlen(ptr);
 				}
 			}
 			++ptr;