[PATCH v2] bcachefs: Fix NULL pointer dereference in bch2_opt_to_text

[Mohammed Anees]

In this patch, I added a proper bounds check to avoid a potential NULL
pointer dereference when opt->choices[v] is accessed in the
bch2_opt_to_text function. This ensures that v is within the valid
range of choices.

Reported-and-tested-by: syzbot+37186860aa7812b331d5@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=37186860aa7812b331d5
Signed-off-by: Mohammed Anees <pvmohammedanees2003@xxxxxxxxx>
---

v2:
- Replaced pr_err with prt_printf as suggested.
- Added the bounds check on opt->choices before accessing it.

 fs/bcachefs/opts.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c
index e10fc1da7..9bb15694d 100644
--- a/fs/bcachefs/opts.c
+++ b/fs/bcachefs/opts.c
@@ -420,8 +420,12 @@ void bch2_opt_to_text(struct printbuf *out,
 	case BCH_OPT_STR:
 		if (flags & OPT_SHOW_FULL_LIST)
 			prt_string_option(out, opt->choices, v);
-		else
-			prt_str(out, opt->choices[v]);
+		else {
+			if (v < opt->min || v >= opt->max - 1)
+				prt_printf(out, "(invalid option %lli)", v);
+			else
+				prt_str(out, opt->choices[v]);
+		}
 		break;
 	case BCH_OPT_FN:
 		opt->fn.to_text(out, c, sb, v);
-- 
2.46.0