[syzbot] [jfs?] KASAN: slab-out-of-bounds Write in diWrite

[syzbot] [jfs?] KASAN: slab-out-of-bounds Write in diWrite

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7b4f2bc91c15 Add linux-next specific files for 20240418
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1181b910980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ae644165a243bf62
dashboard link: https://syzkaller.appspot.com/bug?extid=aa6df9d3b383bf5f047f
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=108f21c7180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=128532bb180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/524a18e6c5be/disk-7b4f2bc9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/029f1b84d653/vmlinux-7b4f2bc9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c02d1542e886/bzImage-7b4f2bc9.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/b09f946202a4/mount_0.gz

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10dec06b180000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12dec06b180000
console output: https://syzkaller.appspot.com/x/log.txt?x=14dec06b180000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aa6df9d3b383bf5f047f@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
==================================================================
BUG: KASAN: use-after-free in diWrite+0xde3/0x19b0 fs/jfs/jfs_imap.c:750
Write of size 32 at addr ffff888076cee0c0 by task syz-executor949/5083

CPU: 1 PID: 5083 Comm: syz-executor949 Not tainted 6.9.0-rc4-next-20240418-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
 diWrite+0xde3/0x19b0 fs/jfs/jfs_imap.c:750
 txCommit+0xa1a/0x6a20 fs/jfs/jfs_txnmgr.c:1255
 add_missing_indices fs/jfs/jfs_dtree.c:2661 [inline]
 jfs_readdir+0x28e9/0x4660 fs/jfs/jfs_dtree.c:3009
 wrap_directory_iterator+0x94/0xe0 fs/readdir.c:67
 iterate_dir+0x65e/0x820 fs/readdir.c:110
 __do_sys_getdents64 fs/readdir.c:409 [inline]
 __se_sys_getdents64+0x20d/0x4f0 fs/readdir.c:394
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff57c567679
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffddcb47e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fffddcb49b8 RCX: 00007ff57c567679
RDX: 000000000000005d RSI: 00000000200002c0 RDI: 0000000000000005
RBP: 00007ff57c5e0610 R08: 0000000000000000 R09: 00007fffddcb49b8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fffddcb49a8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x76cee
flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff)
raw: 00fff80000000000 ffffea0001db3bc8 ffffea0001dcea48 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x500cc2(GFP_HIGHUSER|__GFP_ACCOUNT), pid 5078, tgid 397447660 (sshd), ts 5078, free_ts 51945391130
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1476
 prep_new_page mm/page_alloc.c:1484 [inline]
 get_page_from_freelist+0x2ce2/0x2d90 mm/page_alloc.c:3446
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4704
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 pipe_write+0x657/0x1a40 fs/pipe.c:513
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa72/0xc90 fs/read_write.c:590
 ksys_write+0x1a0/0x2c0 fs/read_write.c:643
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5080 tgid 5080 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1096 [inline]
 free_unref_page+0xd22/0xea0 mm/page_alloc.c:2609
 __folio_put+0x3b9/0x620 mm/swap.c:129
 pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
 pipe_update_tail fs/pipe.c:224 [inline]
 pipe_read+0x6f2/0x13e0 fs/pipe.c:344
 new_sync_read fs/read_write.c:395 [inline]
 vfs_read+0x9c4/0xbd0 fs/read_write.c:476
 ksys_read+0x1a0/0x2c0 fs/read_write.c:619
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888076cedf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888076cee000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888076cee080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888076cee100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888076cee180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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Re: [syzbot] [syzbot] [jfs?] KASAN: slab-out-of-bounds Write in diWrite

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [syzbot] [jfs?] KASAN: slab-out-of-bounds Write in diWrite
Author: lizhi.xu@windriver.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git ed30a4a51bb1

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 2ec35889ad24..84c9abb0fa71 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -746,7 +746,9 @@ int diWrite(tid_t tid, struct inode *ip)
 		p = (dtpage_t *) &jfs_ip->i_dtroot;
 		xp = (dtpage_t *) & dp->di_dtroot;
 		lv = ilinelock->lv;
-		for (n = 0; n < ilinelock->index; n++, lv++) {
+		printk("sp ms: %d, dp ms: %d, %s\n", p->header.maxslot, xp->header.maxslot, __func__);
+		if (p->header.maxslot < DTPAGEMAXSLOT && xp->header.maxslot < DTPAGEMAXSLOT)
+		for (n = 0; n < ilinelock->index && lv->offset < DTPAGEMAXSLOT; n++, lv++) {
 			memcpy(&xp->slot[lv->offset], &p->slot[lv->offset],
 			       lv->length << L2DTSLOTSIZE);
 		}

Re: [syzbot] [syzbot] [jfs?] KASAN: slab-out-of-bounds Write in diWrite

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [syzbot] [jfs?] KASAN: slab-out-of-bounds Write in diWrite
Author: lizhi.xu@windriver.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git ed30a4a51bb1

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 2ec35889ad24..d9b302938ed2 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -747,6 +747,8 @@ int diWrite(tid_t tid, struct inode *ip)
 		xp = (dtpage_t *) & dp->di_dtroot;
 		lv = ilinelock->lv;
 		for (n = 0; n < ilinelock->index; n++, lv++) {
+			printk("lv: %p offset:%d %s\n", lv, lv->offset, __func__);
+			if (lv->offset < DTPAGEMAXSLOT)
 			memcpy(&xp->slot[lv->offset], &p->slot[lv->offset],
 			       lv->length << L2DTSLOTSIZE);
 		}

Forwarded: Re: [syz] KASAN: slab-out-of-bounds Write in diWrite

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syz] KASAN: slab-out-of-bounds Write in diWrite
Author: tristmd@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

>From b49fd6df859312590dfffd12e3dad87914f88c9c Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Thu, 30 Apr 2026 23:01:32 +0000
Subject: [PATCH] jfs: validate lv bounds in diWrite to prevent
 slab-out-of-bounds

diWrite() copies btree root data from the in-memory inode to the
on-disk dinode using lv->offset and lv->length from the transaction
lock without bounds checking.  When a corrupted JFS filesystem image
provides inconsistent dtree or xtree metadata, the transaction log
entries can reference slots beyond the root node boundaries
(DTROOTMAXSLOT or XTROOTMAXSLOT), causing a slab-out-of-bounds write
in the subsequent memcpy.

For example, with a crafted directory inode where the dtree metadata
produces lv->offset + lv->length > DTROOTMAXSLOT (9), the memcpy in
the dtree copy loop writes 32 bytes past the dinode boundary into
adjacent slab memory.

Add bounds validation before each memcpy in both the xtree and dtree
copy loops to ensure lv->offset + lv->length does not exceed
XTROOTMAXSLOT (18) or DTROOTMAXSLOT (9) respectively.

Reported-by: syzbot+aa6df9d3b383bf5f047f@syzkaller.appspotmail.com
Fixes: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
 fs/jfs/jfs_imap.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index b84ba4d7dfb44..70d6a33597273 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -726,6 +726,11 @@ int diWrite(tid_t tid, struct inode *ip)
 		xp = &dp->di_xtroot;
 		lv = ilinelock->lv;
 		for (n = 0; n < ilinelock->index; n++, lv++) {
+			if (lv->offset + lv->length > XTROOTMAXSLOT) {
+				jfs_err("diWrite: xtree lv out of bounds");
+				release_metapage(mp);
+				return -EIO;
+			}
 			memcpy(&xp->xad[lv->offset], &p->xad[lv->offset],
 			       lv->length << L2XTSLOTSIZE);
 		}
@@ -750,6 +755,11 @@ int diWrite(tid_t tid, struct inode *ip)
 		xp = (dtpage_t *) & dp->di_dtroot;
 		lv = ilinelock->lv;
 		for (n = 0; n < ilinelock->index; n++, lv++) {
+			if (lv->offset + lv->length > DTROOTMAXSLOT) {
+				jfs_err("diWrite: dtree lv out of bounds");
+				release_metapage(mp);
+				return -EIO;
+			}
 			memcpy(&xp->slot[lv->offset], &p->slot[lv->offset],
 			       lv->length << L2DTSLOTSIZE);
 		}
--
2.47.3