file: fix segfault in uci_parse_option

Fixed a segmentation fault caused by using a pointer to a reallocated
address. The name pointer in the uci_parse_option function
becomes invalid if assert_eol calls uci_realloc down the line,
resulting in a segmentation fault when attempting to dereference
name in a strcmp check in uci_lookup_list. 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 3cd7702fe260e85b3368848791472d1419eab2f9..3ac49c6edaf31eb081e805329605adc05502cf4d 100644 (file)
--- a/file.c
+++ b/file.c
@@ -471,9 +471,9 @@ static void uci_parse_option(struct uci_context *ctx, bool list)
 
        ofs_name = next_arg(ctx, true, true, false);
        ofs_value = next_arg(ctx, false, false, false);
+       assert_eol(ctx);
        name = pctx_str(pctx, ofs_name);
        value = pctx_str(pctx, ofs_value);
-       assert_eol(ctx);
 
        uci_fill_ptr(ctx, &ptr, &pctx->section->e);
        e = uci_lookup_list(&pctx->section->options, name);