file: fix segfault in uci_parse_config

Fixed a segmentation fault caused by using a pointer to a reallocated
address. The name pointer in the uci_parse_config function
becomes invalid if assert_eol calls uci_realloc down the line,
resulting in a segmentation fault when attempting to dereference
name. A simple fix is to call assert_eol before retrieving the
actual address for the name and type pointers.

The segmentation fault has been found while fuzzing the
uci configuration system for various types of different crashes
and undefined behavious, which resulted in multiple different
import files causing instability and sementation faults.

Signed-off-by: Luka Kožnjak <luka.koznjak@sartura.hr>
Signed-off-by: Juraj Vijtiuk <juraj.vijtiuk@sartura.hr>
CC: Luka Perkov <luka.perkov@sartura.hr>

diff --git a/file.c b/file.c
index f5032bd12847fc8ebdd6132d2293803aefe4aad0..3cd7702fe260e85b3368848791472d1419eab2f9 100644 (file)
--- a/file.c
+++ b/file.c
@@ -425,9 +425,9 @@ static void uci_parse_config(struct uci_context *ctx)
                uci_parse_error(ctx, "invalid character in type field");
 
        ofs_name = next_arg(ctx, false, true, false);
+       assert_eol(ctx);
        type = pctx_str(pctx, ofs_type);
        name = pctx_str(pctx, ofs_name);
-       assert_eol(ctx);
 
        if (!name || !name[0]) {
                ctx->internal = !pctx->merge;