linux-kernel - [PATCH resend v3] bcachefs: Fix NULL pointer dereference in bch2_opt_to

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Message-ID: <20241005130229.9290-1-pvmohammedanees2003@gmail.com>
Date: Sat,  5 Oct 2024 18:32:29 +0530
From: Mohammed Anees <pvmohammedanees2003@...il.com>
To: linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Kent Overstreet <kent.overstreet@...ux.dev>,
	Mohammed Anees <pvmohammedanees2003@...il.com>,
	syzbot+37186860aa7812b331d5@...kaller.appspotmail.com
Subject: [PATCH resend v3] bcachefs: Fix NULL pointer dereference in bch2_opt_to_text

This patch adds a bounds check to the bch2_opt_to_text function to prevent
NULL pointer dereferences when accessing the opt->choices array. This
ensures that the index used is within valid bounds before dereferencing.
The new version enhances the readability.

Reported-and-tested-by: syzbot+37186860aa7812b331d5@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=37186860aa7812b331d5
Signed-off-by: Mohammed Anees <pvmohammedanees2003@...il.com>
---
v3:
- Moved bounds check above as default case.
- Removed the nesterd if clauses.
---
 fs/bcachefs/opts.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c
index 232be8a44051..84097235eea9 100644
--- a/fs/bcachefs/opts.c
+++ b/fs/bcachefs/opts.c
@@ -427,7 +427,9 @@ void bch2_opt_to_text(struct printbuf *out,
 			prt_printf(out, "%lli", v);
 		break;
 	case BCH_OPT_STR:
-		if (flags & OPT_SHOW_FULL_LIST)
+		if (v < opt->min || v >= opt->max - 1)
+			prt_printf(out, "(invalid option %lli)", v);
+		else if (flags & OPT_SHOW_FULL_LIST)
 			prt_string_option(out, opt->choices, v);
 		else
 			prt_str(out, opt->choices[v]);
-- 
2.46.0