libcom_err: Fix sign-extension problem on 64-bit systems in error_message()

On 64-bit systems (or anything with sizeof(long) > sizeof(int)), we
sometimes get error codes passed to error_message which have been cast
from an (int) to an (unsigned int). This almost always happens if
you're using libgssapi_krb5, which returns an error code which is less
than 0 but is returned in an (unsigned int).

For example, -1765328377L gets cast to 2529638919, which is
0x96c73a07, not 0xffffffff96c73a07, so error_message() fails to find a
matching error table.

When error_message() then calls the error_table_name() function to get a
name to use in the "unknown code" message, it gets a correct value back.

This happens because error_table_name() drops most of the higher bits of
the parameter it's passed before doing anything else with it (& 077777777f,
or & 0xffffff). If we did the same thing in error_message(), we wouldn't
have a problem there, either.

Problem reported and fixed by: Nalin Dahyabhai

Addresses-Sourceforge-Bug: #1809658

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/et/error_message.c b/lib/et/error_message.c
index 4e84e35..708dd2f 100644 (file)
--- a/lib/et/error_message.c
+++ b/lib/et/error_message.c
@@ -69,7 +69,7 @@ const char * error_message (errcode_t code)
 #endif
     }
     for (et = _et_list; et; et = et->next) {
-       if (et->table->base == table_num) {
+       if ((et->table->base & 0xffffffL) == (table_num & 0xffffffL)) {
            /* This is the right table */
            if (et->table->n_msgs <= offset)
                goto oops;
@@ -77,7 +77,7 @@ const char * error_message (errcode_t code)
        }
     }
     for (et = _et_dynamic_list; et; et = et->next) {
-       if (et->table->base == table_num) {
+       if ((et->table->base & 0xffffffL) == (table_num & 0xffffffL)) {
            /* This is the right table */
            if (et->table->n_msgs <= offset)
                goto oops;