linux-kernel - Re: [syzbot] [block?] general protection fault in bio_iov_iter_get

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Message-ID: <20250907081937.6583-1-hdanton@sina.com>
Date: Sun,  7 Sep 2025 16:19:36 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+b253ade8e1751d90a7a9@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] general protection fault in bio_iov_iter_get_pages

> Date: Sun, 07 Sep 2025 00:11:35 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    be5d4872e528 Add linux-next specific files for 20250905
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17896962580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a726684450a7d788
> dashboard link: https://syzkaller.appspot.com/bug?extid=b253ade8e1751d90a7a9
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10496962580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14a98962580000

#syz test

--- x/mm/gup.c
+++ y/mm/gup.c
@@ -2981,6 +2981,7 @@ static int gup_fast_pmd_leaf(pmd_t orig,
 		return 0;
 	}
 
+	pages += *nr;
 	*nr += refs;
 	for (; refs; refs--)
 		*(pages++) = page++;
@@ -3024,6 +3025,7 @@ static int gup_fast_pud_leaf(pud_t orig,
 		return 0;
 	}
 
+	pages += *nr;
 	*nr += refs;
 	for (; refs; refs--)
 		*(pages++) = page++;
--