[syzbot] [xfs?] KASAN: use-after-free Read in hpfs_bplus_lookup

[syzbot] [xfs?] KASAN: use-after-free Read in hpfs_bplus_lookup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    b71e635feefc Merge tag 'cgroup-for-6.19-rc5-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10efa99a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7b058fb1d7dbe6b1
dashboard link: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
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=10cd15fa580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=152a4052580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/40abbbbc34a8/disk-b71e635f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/74edfb8073f7/vmlinux-b71e635f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3b5198043bfa/bzImage-b71e635f.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/7f1692afbc9c/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1609599a580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/d09b0f5dc58e/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com

hpfs: filesystem error: invalid number of hotfixes: 2066844986, used: 2066844985; already mounted read-only
hpfs: filesystem error: improperly stopped
hpfs: filesystem error: warning: spare dnodes used, try chkdsk
hpfs: You really don't want any checks? You are crazy...
hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
hpfs: filesystem error: map_dirent: not a directory
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: filesystem error: unable to find root dir
==================================================================
BUG: KASAN: use-after-free in hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
Read of size 4 at addr ffff888052abe004 by task syz.0.27/6198

CPU: 1 UID: 0 PID: 6198 Comm: syz.0.27 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
 hpfs_bmap+0x22a/0x4d0 fs/hpfs/file.c:54
 hpfs_get_block+0xa8/0x6e0 fs/hpfs/file.c:87
 do_mpage_readpage+0x822/0x1990 fs/mpage.c:222
 mpage_readahead+0x3b0/0x790 fs/mpage.c:371
 read_pages+0x17a/0x580 mm/readahead.c:163
 page_cache_ra_unbounded+0x68b/0x8c0 mm/readahead.c:302
 filemap_get_pages+0x446/0x1ee0 mm/filemap.c:2690
 filemap_read+0x3f9/0x11a0 mm/filemap.c:2800
 __kernel_read+0x4d8/0x970 fs/read_write.c:530
 integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
 ima_calc_file_hash+0x86a/0x1700 security/integrity/ima/ima_crypto.c:568
 ima_collect_measurement+0x42e/0x900 security/integrity/ima/ima_api.c:293
 process_measurement+0x112a/0x1a80 security/integrity/ima/ima_main.c:406
 ima_file_check+0xd9/0x130 security/integrity/ima/ima_main.c:663
 security_file_post_open+0xbb/0x290 security/security.c:2652
 do_open fs/namei.c:4639 [inline]
 path_openat+0x3472/0x3df0 fs/namei.c:4796
 do_filp_open+0x1fa/0x410 fs/namei.c:4823
 do_sys_openat2+0x121/0x200 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb59539f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff3ac53cb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fb5955f5fa0 RCX: 00007fb59539f749
RDX: 0000000000000000 RSI: 0000200000004280 RDI: ffffffffffffff9c
RBP: 00007fb595423f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb5955f5fa0 R14: 00007fb5955f5fa0 R15: 0000000000000004
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb58c615 pfn:0x52abe
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea00014aafc8 ffff8880b8842d30 0000000000000000
raw: 00000007fb58c615 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 6198, tgid 6198 (syz.0.27), ts 130045840131, free_ts 130049000115
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
 vma_alloc_folio_noprof+0xe4/0x280 mm/mempolicy.c:2540
 folio_prealloc+0x30/0x180 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:5165 [inline]
 do_anonymous_page mm/memory.c:5222 [inline]
 do_pte_missing+0x86a/0x27a0 mm/memory.c:4399
 handle_pte_fault mm/memory.c:6273 [inline]
 __handle_mm_fault mm/memory.c:6411 [inline]
 handle_mm_fault+0xcc1/0x1330 mm/memory.c:6580
 do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
page last free pid 6198 tgid 6198 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
 folios_put_refs+0x569/0x670 mm/swap.c:1002
 free_pages_and_swap_cache+0x4be/0x520 mm/swap_state.c:358
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
 tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
 vms_clear_ptes+0x42b/0x530 mm/vma.c:1238
 vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1280
 do_vmi_align_munmap+0x372/0x450 mm/vma.c:1539
 do_vmi_munmap+0x253/0x2e0 mm/vma.c:1587
 __vm_munmap+0x207/0x380 mm/vma.c:3203
 __do_sys_munmap mm/mmap.c:1077 [inline]
 __se_sys_munmap mm/mmap.c:1074 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1074
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888052abdf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888052abdf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888052abe000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888052abe080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888052abe100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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Forwarded: [PATCH] hpfs: add buffer bounds validation in hpfs_bplus_lookup

[syzbot]

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

***

Subject: [PATCH] hpfs: add buffer bounds validation in hpfs_bplus_lookup
Author: kartikey406@gmail.com


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

When traversing the B+ tree in a corrupted HPFS filesystem, the btree
pointer obtained from GET_BTREE_PTR() may point outside the mapped
buffer's bounds if the on-disk data structures are malformed. This
leads to a use-after-free when accessing btree->u.external[i] as the
memory may have been freed and reallocated.

Additionally, a corrupted n_used_nodes value can cause out-of-bounds
array access when iterating through btree->u.internal[] or
btree->u.external[] arrays.

Add validation to ensure:
1. The btree pointer stays within the mapped buffer boundaries
2. The n_used_nodes value is within reasonable limits

This prevents KASAN-detected use-after-free when processing malicious
HPFS filesystem images.

Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/hpfs/anode.c | XX insertions(+), X deletions(-)

diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c
index XXXXXXX..YYYYYYY 100644
--- a/fs/hpfs/anode.c
+++ b/fs/hpfs/anode.c
@@ -XX,6 +XX,16 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 				brelse(bh);
 				if (!(anode = hpfs_map_anode(s
---
 fs/hpfs/anode.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 71 insertions(+), 3 deletions(-)

diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c
index a4f5321eafae..826e2142223b 100644
--- a/fs/hpfs/anode.c
+++ b/fs/hpfs/anode.c
@@ -19,25 +19,87 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 	struct anode *anode;
 	int i;
 	int c1, c2 = 0;
+	
+	printk(KERN_DEBUG "hpfs_bplus_lookup: ENTRY btree=%px bh=%px sec=%u\n", 
+	       btree, bh, sec);
+	
 	go_down:
 	if (hpfs_sb(s)->sb_chk) if (hpfs_stop_cycles(s, a, &c1, &c2, "hpfs_bplus_lookup")) return -1;
+	
+	printk(KERN_DEBUG "hpfs_bplus_lookup: go_down - btree=%px bh=%px internal=%d n_used_nodes=%u\n",
+	       btree, bh, bp_internal(btree), btree->n_used_nodes);
+	
 	if (bp_internal(btree)) {
-		for (i = 0; i < btree->n_used_nodes; i++)
+		printk(KERN_DEBUG "hpfs_bplus_lookup: Processing INTERNAL node\n");
+		for (i = 0; i < btree->n_used_nodes; i++) {
+			printk(KERN_DEBUG "hpfs_bplus_lookup: internal[%d] file_secno=%u looking_for=%u\n",
+			       i, le32_to_cpu(btree->u.internal[i].file_secno), sec);
+			
 			if (le32_to_cpu(btree->u.internal[i].file_secno) > sec) {
 				a = le32_to_cpu(btree->u.internal[i].down);
+				
+				printk(KERN_DEBUG "hpfs_bplus_lookup: Found match, going down to anode=%08x\n", a);
+				printk(KERN_DEBUG "hpfs_bplus_lookup: BEFORE brelse - bh=%px btree=%px\n", bh, btree);
+				
 				brelse(bh);
-				if (!(anode = hpfs_map_anode(s, a, &bh))) return -1;
+				
+				printk(KERN_DEBUG "hpfs_bplus_lookup: AFTER brelse - calling hpfs_map_anode\n");
+				
+				if (!(anode = hpfs_map_anode(s, a, &bh))) {
+					printk(KERN_ERR "hpfs_bplus_lookup: hpfs_map_anode FAILED for anode=%08x\n", a);
+					return -1;
+				}
+				
+				printk(KERN_DEBUG "hpfs_bplus_lookup: hpfs_map_anode SUCCESS - new_bh=%px anode=%px\n", bh, anode);
+				
 				btree = GET_BTREE_PTR(&anode->btree);
+				/* Validate btree pointer is within buffer bounds */
+				if ((unsigned long)btree < (unsigned long)bh->b_data ||
+    					(unsigned long)btree + sizeof(*btree) > (unsigned long)bh->b_data + bh->b_size) {
+    					printk(KERN_ERR "hpfs_bplus_lookup: INVALID btree pointer! btree=%px buf_start=%px buf_end=%px\n",
+           					btree, bh->b_data, (void *)((unsigned long)bh->b_data + bh->b_size));
+    					brelse(bh);
+    					return -1;
+				}
+
+				/* Validate n_used_nodes is reasonable */
+				if (btree->n_used_nodes > 100) {  /* Adjust based on actual max */
+    					printk(KERN_ERR "hpfs_bplus_lookup: SUSPICIOUS n_used_nodes=%u (too large)\n",
+           					btree->n_used_nodes);
+    					brelse(bh);
+    					return -1;
+				}				
+				printk(KERN_DEBUG "hpfs_bplus_lookup: NEW btree=%px (from anode->btree)\n", btree);
+				
 				goto go_down;
 			}
+		}
 		hpfs_error(s, "sector %08x not found in internal anode %08x", sec, a);
 		brelse(bh);
 		return -1;
 	}
-	for (i = 0; i < btree->n_used_nodes; i++)
+	
+	printk(KERN_DEBUG "hpfs_bplus_lookup: Processing EXTERNAL node - btree=%px bh=%px n_used_nodes=%u\n",
+	       btree, bh, btree->n_used_nodes);
+	
+	/* Add bounds checking */
+	printk(KERN_DEBUG "hpfs_bplus_lookup: Buffer bounds - bh->b_data=%px size=%zu btree=%px\n",
+	       bh->b_data, bh->b_size, btree);
+	
+	for (i = 0; i < btree->n_used_nodes; i++) {
+		printk(KERN_DEBUG "hpfs_bplus_lookup: external[%d] - accessing btree->u.external[%d] at %px\n",
+		       i, i, &btree->u.external[i]);
+		
+		/* This is line 38 - the crash point */
+		printk(KERN_DEBUG "hpfs_bplus_lookup: external[%d] - reading file_secno from %px\n",
+		       i, &btree->u.external[i].file_secno);
+		
 		if (le32_to_cpu(btree->u.external[i].file_secno) <= sec &&
 		    le32_to_cpu(btree->u.external[i].file_secno) + le32_to_cpu(btree->u.external[i].length) > sec) {
 			a = le32_to_cpu(btree->u.external[i].disk_secno) + sec - le32_to_cpu(btree->u.external[i].file_secno);
+			
+			printk(KERN_DEBUG "hpfs_bplus_lookup: FOUND external match - disk_secno=%u\n", a);
+			
 			if (hpfs_sb(s)->sb_chk) if (hpfs_chk_sectors(s, a, 1, "data")) {
 				brelse(bh);
 				return -1;
@@ -49,10 +111,16 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 				hpfs_inode->i_n_secs = le32_to_cpu(btree->u.external[i].length);
 			}
 			brelse(bh);
+			
+			printk(KERN_DEBUG "hpfs_bplus_lookup: EXIT SUCCESS - returning %u\n", a);
 			return a;
 		}
+	}
+	
 	hpfs_error(s, "sector %08x not found in external anode %08x", sec, a);
 	brelse(bh);
+	
+	printk(KERN_DEBUG "hpfs_bplus_lookup: EXIT FAILURE\n");
 	return -1;
 }
 
-- 
2.43.0

Forwarded: [PATCH] hpfs: add buffer bounds validation in hpfs_bplus_lookup

[syzbot]

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

***

Subject: [PATCH] hpfs: add buffer bounds validation in hpfs_bplus_lookup
Author: kartikey406@gmail.com

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

When traversing the B+ tree in a corrupted HPFS filesystem, the btree
pointer obtained from GET_BTREE_PTR() may point outside the mapped
buffer's bounds if the on-disk data structures are malformed. This
leads to a use-after-free when accessing btree->u.external[i] as the
memory may have been freed and reallocated.

Additionally, a corrupted n_used_nodes value can cause out-of-bounds
array access when iterating through btree->u.internal[] or
btree->u.external[] arrays.

Add validation to ensure:
1. The btree pointer stays within the mapped buffer boundaries
2. The n_used_nodes value is within reasonable limits

This prevents KASAN-detected use-after-free when processing malicious
HPFS filesystem images.

Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
---
 fs/hpfs/anode.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c
index a4f5321eafae..7324ec22941a 100644
--- a/fs/hpfs/anode.c
+++ b/fs/hpfs/anode.c
@@ -28,6 +28,18 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 				brelse(bh);
 				if (!(anode = hpfs_map_anode(s, a, &bh))) return -1;
 				btree = GET_BTREE_PTR(&anode->btree);
+				if ((void *)btree < (void *)bh->b_data ||
+				    (void *)btree + sizeof(*btree) > (void *)bh->b_data + bh->b_size) {
+					hpfs_error(s, "btree pointer out of bounds");
+					brelse(bh);
+					return -1;
+				}
+
+				if (btree->n_used_nodes > 60) {
+					hpfs_error(s, "n_used_nodes=%u is suspiciously large", btree->n_used_nodes);
+					brelse(bh);
+					return -1;
+				}
 				goto go_down;
 			}
 		hpfs_error(s, "sector %08x not found in internal anode %08x", sec, a);
-- 
2.43.0

Forwarded: [PATCH] hpfs: add debug logging to hpfs_bplus_lookup

[syzbot]

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

***

Subject: [PATCH] hpfs: add debug logging to hpfs_bplus_lookup
Author: kartikey406@gmail.com

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


This is a debug patch to understand the use-after-free issue reported
by syzbot. It adds extensive logging to track:
- Buffer head addresses and lifecycle
- btree pointer values and offsets
- Array access patterns before crashes
- Internal vs external node processing

This will help identify exactly where and why the use-after-free occurs.

NOT FOR MERGE - DEBUG ONLY

Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb"
---
 fs/hpfs/anode.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c
index a4f5321eafae..e55d0f5fd782 100644
--- a/fs/hpfs/anode.c
+++ b/fs/hpfs/anode.c
@@ -19,25 +19,57 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 	struct anode *anode;
 	int i;
 	int c1, c2 = 0;
+
+	printk(KERN_EMERG "=== BPLUS_LOOKUP ENTRY: btree=%px bh=%px bh->b_data=%px sec=%u ===\n",
+	       btree, bh, bh->b_data, sec);
 	go_down:
+	printk(KERN_EMERG "=== go_down: btree=%px bh=%px n_used_nodes=%u internal=%d ===\n",
+	       btree, bh, btree->n_used_nodes, bp_internal(btree));
+
 	if (hpfs_sb(s)->sb_chk) if (hpfs_stop_cycles(s, a, &c1, &c2, "hpfs_bplus_lookup")) return -1;
 	if (bp_internal(btree)) {
-		for (i = 0; i < btree->n_used_nodes; i++)
+		printk(KERN_EMERG "=== Processing INTERNAL node, n_used_nodes=%u ===\n", btree->n_used_nodes);
+		for (i = 0; i < btree->n_used_nodes; i++) {
+			printk(KERN_EMERG "=== internal[%d]: accessing %px ===\n", i, &btree->u.internal[i]);
 			if (le32_to_cpu(btree->u.internal[i].file_secno) > sec) {
 				a = le32_to_cpu(btree->u.internal[i].down);
+				printk(KERN_EMERG "=== Found match, going to anode=%08x ===\n", a);
+				printk(KERN_EMERG "=== RELEASING bh=%px ===\n", bh);
+
 				brelse(bh);
-				if (!(anode = hpfs_map_anode(s, a, &bh))) return -1;
+				printk(KERN_EMERG "=== Calling hpfs_map_anode for %08x ===\n", a);
+
+				if (!(anode = hpfs_map_anode(s, a, &bh))){
+					printk(KERN_EMERG "=== hpfs_map_anode FAILED ===\n");
+					return -1;
+				}
+				printk(KERN_EMERG "=== hpfs_map_anode SUCCESS: anode=%px new_bh=%px new_bh->b_data=%px ===\n",
+				       anode, bh, bh->b_data);
+
 				btree = GET_BTREE_PTR(&anode->btree);
+
+				printk(KERN_EMERG "=== NEW btree=%px (offset from b_data: %ld) ===\n",
+				       btree, (long)((void *)btree - (void *)bh->b_data));
+				printk(KERN_EMERG "=== Validation passed, jumping to go_down ===\n");
 				goto go_down;
 			}
+		}
 		hpfs_error(s, "sector %08x not found in internal anode %08x", sec, a);
 		brelse(bh);
 		return -1;
 	}
-	for (i = 0; i < btree->n_used_nodes; i++)
+
+	printk(KERN_EMERG "=== Processing EXTERNAL node, n_used_nodes=%u ===\n", btree->n_used_nodes);
+	printk(KERN_EMERG "=== btree=%px bh=%px bh->b_data=%px bh->b_size=%zu ===\n",
+	       btree, bh, bh->b_data, bh->b_size);
+	for (i = 0; i < btree->n_used_nodes; i++) {
+		printk(KERN_EMERG "=== external[%d]: about to access %px ===\n", i, &btree->u.external[i]);
+		printk(KERN_EMERG "=== CRASH WILL HAPPEN ON NEXT LINE IF UAF ===\n");
 		if (le32_to_cpu(btree->u.external[i].file_secno) <= sec &&
 		    le32_to_cpu(btree->u.external[i].file_secno) + le32_to_cpu(btree->u.external[i].length) > sec) {
 			a = le32_to_cpu(btree->u.external[i].disk_secno) + sec - le32_to_cpu(btree->u.external[i].file_secno);
+
+			printk(KERN_EMERG "=== Found external match, returning %u ===\n", a);
 			if (hpfs_sb(s)->sb_chk) if (hpfs_chk_sectors(s, a, 1, "data")) {
 				brelse(bh);
 				return -1;
@@ -51,6 +83,7 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 			brelse(bh);
 			return a;
 		}
+	}
 	hpfs_error(s, "sector %08x not found in external anode %08x", sec, a);
 	brelse(bh);
 	return -1;
-- 
2.43.0

Forwarded: [PATCH] hpfs: add array bounds validation in hpfs_bplus_lookup

[syzbot]

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

***

Subject: [PATCH] hpfs: add array bounds validation in hpfs_bplus_lookup
Author: kartikey406@gmail.com

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


When traversing a corrupted HPFS filesystem, the n_used_nodes field in
the btree header can contain a value larger than what fits in the
allocated buffer. This causes out-of-bounds array access when iterating
through btree->u.internal[] or btree->u.external[] arrays, leading to
a KASAN-detected use-after-free.

Validate that n_used_nodes does not exceed the maximum number of nodes
that can fit in the buffer before accessing the arrays.

Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/hpfs/anode.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c
index a4f5321eafae..6e1b43f5c9cf 100644
--- a/fs/hpfs/anode.c
+++ b/fs/hpfs/anode.c
@@ -21,6 +22,31 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode,
 	int c1, c2 = 0;
 	go_down:
 	if (hpfs_sb(s)->sb_chk) if (hpfs_stop_cycles(s, a, &c1, &c2, "hpfs_bplus_lookup")) return -1;
+
+	if (bp_internal(btree)) {
+		unsigned int max_internal_nodes;
+
+		max_internal_nodes = (bh->b_size - ((char *)btree->u.internal - (char *)bh->b_data))
+				      / sizeof(btree->u.internal[0]);
+		if (btree->n_used_nodes > max_internal_nodes) {
+			hpfs_error(s, "btree->n_used_nodes = %u, but max for internal node is %u",
+				   btree->n_used_nodes, max_internal_nodes);
+			brelse(bh);
+			return -1;
+		}
+	} else {
+		unsigned int max_external_nodes;
+
+		max_external_nodes = (bh->b_size - ((char *)btree->u.external - (char *)bh->b_data))
+				     / sizeof(btree->u.external[0]);
+		if (btree->n_used_nodes > max_external_nodes) {
+			hpfs_error(s, "btree->n_used_nodes = %u, but max for external node is %u",
+				   btree->n_used_nodes, max_external_nodes);
+			brelse(bh);
+			return -1;
+		}
+	}
+
 	if (bp_internal(btree)) {
 		for (i = 0; i < btree->n_used_nodes; i++)
 			if (le32_to_cpu(btree->u.internal[i].file_secno) > sec) {
-- 
2.43.0

Re: [syzbot] [xfs?] KASAN: use-after-free Read in hpfs_bplus_lookup

[Christoph Hellwig]

Any idea why this Ccs the xfs list?

On Fri, Jan 16, 2026 at 01:04:26PM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    b71e635feefc Merge tag 'cgroup-for-6.19-rc5-fixes' of git:..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10efa99a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7b058fb1d7dbe6b1
> dashboard link: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
> 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=10cd15fa580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=152a4052580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/40abbbbc34a8/disk-b71e635f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/74edfb8073f7/vmlinux-b71e635f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/3b5198043bfa/bzImage-b71e635f.xz
> mounted in repro #1: https://storage.googleapis.com/syzbot-assets/7f1692afbc9c/mount_0.gz
>   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1609599a580000)
> mounted in repro #2: https://storage.googleapis.com/syzbot-assets/d09b0f5dc58e/mount_2.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com
> 
> hpfs: filesystem error: invalid number of hotfixes: 2066844986, used: 2066844985; already mounted read-only
> hpfs: filesystem error: improperly stopped
> hpfs: filesystem error: warning: spare dnodes used, try chkdsk
> hpfs: You really don't want any checks? You are crazy...
> hpfs: hpfs_map_sector(): read error
> hpfs: code page support is disabled
> hpfs: filesystem error: map_dirent: not a directory
> hpfs: hpfs_map_4sectors(): unaligned read
> hpfs: filesystem error: unable to find root dir
> ==================================================================
> BUG: KASAN: use-after-free in hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
> Read of size 4 at addr ffff888052abe004 by task syz.0.27/6198
> 
> CPU: 1 UID: 0 PID: 6198 Comm: syz.0.27 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:378 [inline]
>  print_report+0xca/0x240 mm/kasan/report.c:482
>  kasan_report+0x118/0x150 mm/kasan/report.c:595
>  hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
>  hpfs_bmap+0x22a/0x4d0 fs/hpfs/file.c:54
>  hpfs_get_block+0xa8/0x6e0 fs/hpfs/file.c:87
>  do_mpage_readpage+0x822/0x1990 fs/mpage.c:222
>  mpage_readahead+0x3b0/0x790 fs/mpage.c:371
>  read_pages+0x17a/0x580 mm/readahead.c:163
>  page_cache_ra_unbounded+0x68b/0x8c0 mm/readahead.c:302
>  filemap_get_pages+0x446/0x1ee0 mm/filemap.c:2690
>  filemap_read+0x3f9/0x11a0 mm/filemap.c:2800
>  __kernel_read+0x4d8/0x970 fs/read_write.c:530
>  integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
>  ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
>  ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
>  ima_calc_file_hash+0x86a/0x1700 security/integrity/ima/ima_crypto.c:568
>  ima_collect_measurement+0x42e/0x900 security/integrity/ima/ima_api.c:293
>  process_measurement+0x112a/0x1a80 security/integrity/ima/ima_main.c:406
>  ima_file_check+0xd9/0x130 security/integrity/ima/ima_main.c:663
>  security_file_post_open+0xbb/0x290 security/security.c:2652
>  do_open fs/namei.c:4639 [inline]
>  path_openat+0x3472/0x3df0 fs/namei.c:4796
>  do_filp_open+0x1fa/0x410 fs/namei.c:4823
>  do_sys_openat2+0x121/0x200 fs/open.c:1430
>  do_sys_open fs/open.c:1436 [inline]
>  __do_sys_openat fs/open.c:1452 [inline]
>  __se_sys_openat fs/open.c:1447 [inline]
>  __x64_sys_openat+0x138/0x170 fs/open.c:1447
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fb59539f749
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fff3ac53cb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 00007fb5955f5fa0 RCX: 00007fb59539f749
> RDX: 0000000000000000 RSI: 0000200000004280 RDI: ffffffffffffff9c
> RBP: 00007fb595423f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fb5955f5fa0 R14: 00007fb5955f5fa0 R15: 0000000000000004
>  </TASK>
> 
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb58c615 pfn:0x52abe
> flags: 0x80000000000000(node=0|zone=1)
> raw: 0080000000000000 ffffea00014aafc8 ffff8880b8842d30 0000000000000000
> raw: 00000007fb58c615 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as freed
> page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 6198, tgid 6198 (syz.0.27), ts 130045840131, free_ts 130049000115
>  set_page_owner include/linux/page_owner.h:32 [inline]
>  post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
>  prep_new_page mm/page_alloc.c:1865 [inline]
>  get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
>  __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
>  alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
>  folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
>  vma_alloc_folio_noprof+0xe4/0x280 mm/mempolicy.c:2540
>  folio_prealloc+0x30/0x180 mm/memory.c:-1
>  alloc_anon_folio mm/memory.c:5165 [inline]
>  do_anonymous_page mm/memory.c:5222 [inline]
>  do_pte_missing+0x86a/0x27a0 mm/memory.c:4399
>  handle_pte_fault mm/memory.c:6273 [inline]
>  __handle_mm_fault mm/memory.c:6411 [inline]
>  handle_mm_fault+0xcc1/0x1330 mm/memory.c:6580
>  do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
>  handle_page_fault arch/x86/mm/fault.c:1476 [inline]
>  exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
>  asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
> page last free pid 6198 tgid 6198 stack trace:
>  reset_page_owner include/linux/page_owner.h:25 [inline]
>  free_pages_prepare mm/page_alloc.c:1406 [inline]
>  free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
>  folios_put_refs+0x569/0x670 mm/swap.c:1002
>  free_pages_and_swap_cache+0x4be/0x520 mm/swap_state.c:358
>  __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
>  tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
>  tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
>  tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
>  tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
>  vms_clear_ptes+0x42b/0x530 mm/vma.c:1238
>  vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1280
>  do_vmi_align_munmap+0x372/0x450 mm/vma.c:1539
>  do_vmi_munmap+0x253/0x2e0 mm/vma.c:1587
>  __vm_munmap+0x207/0x380 mm/vma.c:3203
>  __do_sys_munmap mm/mmap.c:1077 [inline]
>  __se_sys_munmap mm/mmap.c:1074 [inline]
>  __x64_sys_munmap+0x60/0x70 mm/mmap.c:1074
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Memory state around the buggy address:
>  ffff888052abdf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff888052abdf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >ffff888052abe000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                    ^
>  ffff888052abe080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff888052abe100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup
> 
---end quoted text---

Re: [syzbot] [xfs?] KASAN: use-after-free Read in hpfs_bplus_lookup

[Aleksandr Nogikh]

On Mon, Jan 19, 2026 at 7:36 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> Any idea why this Ccs the xfs list?

Somehow, the reproducers first mount xfs and only then hpfs, so syzbot
also tagged the xfs list.

>
> On Fri, Jan 16, 2026 at 01:04:26PM -0800, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    b71e635feefc Merge tag 'cgroup-for-6.19-rc5-fixes' of git:..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=10efa99a580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=7b058fb1d7dbe6b1
> > dashboard link: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
> > 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=10cd15fa580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=152a4052580000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/40abbbbc34a8/disk-b71e635f.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/74edfb8073f7/vmlinux-b71e635f.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/3b5198043bfa/bzImage-b71e635f.xz
> > mounted in repro #1: https://storage.googleapis.com/syzbot-assets/7f1692afbc9c/mount_0.gz
> >   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1609599a580000)
> > mounted in repro #2: https://storage.googleapis.com/syzbot-assets/d09b0f5dc58e/mount_2.gz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com
> >
> > hpfs: filesystem error: invalid number of hotfixes: 2066844986, used: 2066844985; already mounted read-only
> > hpfs: filesystem error: improperly stopped
> > hpfs: filesystem error: warning: spare dnodes used, try chkdsk
> > hpfs: You really don't want any checks? You are crazy...
> > hpfs: hpfs_map_sector(): read error
> > hpfs: code page support is disabled
> > hpfs: filesystem error: map_dirent: not a directory
> > hpfs: hpfs_map_4sectors(): unaligned read
> > hpfs: filesystem error: unable to find root dir
> > ==================================================================
> > BUG: KASAN: use-after-free in hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
> > Read of size 4 at addr ffff888052abe004 by task syz.0.27/6198
> >
> > CPU: 1 UID: 0 PID: 6198 Comm: syz.0.27 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
> > Call Trace:
> >  <TASK>
> >  dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> >  print_address_description mm/kasan/report.c:378 [inline]
> >  print_report+0xca/0x240 mm/kasan/report.c:482
> >  kasan_report+0x118/0x150 mm/kasan/report.c:595
> >  hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
> >  hpfs_bmap+0x22a/0x4d0 fs/hpfs/file.c:54
> >  hpfs_get_block+0xa8/0x6e0 fs/hpfs/file.c:87
> >  do_mpage_readpage+0x822/0x1990 fs/mpage.c:222
> >  mpage_readahead+0x3b0/0x790 fs/mpage.c:371
> >  read_pages+0x17a/0x580 mm/readahead.c:163
> >  page_cache_ra_unbounded+0x68b/0x8c0 mm/readahead.c:302
> >  filemap_get_pages+0x446/0x1ee0 mm/filemap.c:2690
> >  filemap_read+0x3f9/0x11a0 mm/filemap.c:2800
> >  __kernel_read+0x4d8/0x970 fs/read_write.c:530
> >  integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
> >  ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
> >  ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
> >  ima_calc_file_hash+0x86a/0x1700 security/integrity/ima/ima_crypto.c:568
> >  ima_collect_measurement+0x42e/0x900 security/integrity/ima/ima_api.c:293
> >  process_measurement+0x112a/0x1a80 security/integrity/ima/ima_main.c:406
> >  ima_file_check+0xd9/0x130 security/integrity/ima/ima_main.c:663
> >  security_file_post_open+0xbb/0x290 security/security.c:2652
> >  do_open fs/namei.c:4639 [inline]
> >  path_openat+0x3472/0x3df0 fs/namei.c:4796
> >  do_filp_open+0x1fa/0x410 fs/namei.c:4823
> >  do_sys_openat2+0x121/0x200 fs/open.c:1430
> >  do_sys_open fs/open.c:1436 [inline]
> >  __do_sys_openat fs/open.c:1452 [inline]
> >  __se_sys_openat fs/open.c:1447 [inline]
> >  __x64_sys_openat+0x138/0x170 fs/open.c:1447
> >  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> >  do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7fb59539f749
> > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007fff3ac53cb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> > RAX: ffffffffffffffda RBX: 00007fb5955f5fa0 RCX: 00007fb59539f749
> > RDX: 0000000000000000 RSI: 0000200000004280 RDI: ffffffffffffff9c
> > RBP: 00007fb595423f91 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > R13: 00007fb5955f5fa0 R14: 00007fb5955f5fa0 R15: 0000000000000004
> >  </TASK>
> >
> > The buggy address belongs to the physical page:
> > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb58c615 pfn:0x52abe
> > flags: 0x80000000000000(node=0|zone=1)
> > raw: 0080000000000000 ffffea00014aafc8 ffff8880b8842d30 0000000000000000
> > raw: 00000007fb58c615 0000000000000000 00000000ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as freed
> > page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 6198, tgid 6198 (syz.0.27), ts 130045840131, free_ts 130049000115
> >  set_page_owner include/linux/page_owner.h:32 [inline]
> >  post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
> >  prep_new_page mm/page_alloc.c:1865 [inline]
> >  get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
> >  __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
> >  alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
> >  folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
> >  vma_alloc_folio_noprof+0xe4/0x280 mm/mempolicy.c:2540
> >  folio_prealloc+0x30/0x180 mm/memory.c:-1
> >  alloc_anon_folio mm/memory.c:5165 [inline]
> >  do_anonymous_page mm/memory.c:5222 [inline]
> >  do_pte_missing+0x86a/0x27a0 mm/memory.c:4399
> >  handle_pte_fault mm/memory.c:6273 [inline]
> >  __handle_mm_fault mm/memory.c:6411 [inline]
> >  handle_mm_fault+0xcc1/0x1330 mm/memory.c:6580
> >  do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
> >  handle_page_fault arch/x86/mm/fault.c:1476 [inline]
> >  exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
> >  asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
> > page last free pid 6198 tgid 6198 stack trace:
> >  reset_page_owner include/linux/page_owner.h:25 [inline]
> >  free_pages_prepare mm/page_alloc.c:1406 [inline]
> >  free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
> >  folios_put_refs+0x569/0x670 mm/swap.c:1002
> >  free_pages_and_swap_cache+0x4be/0x520 mm/swap_state.c:358
> >  __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
> >  tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
> >  tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
> >  tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
> >  tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
> >  vms_clear_ptes+0x42b/0x530 mm/vma.c:1238
> >  vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1280
> >  do_vmi_align_munmap+0x372/0x450 mm/vma.c:1539
> >  do_vmi_munmap+0x253/0x2e0 mm/vma.c:1587
> >  __vm_munmap+0x207/0x380 mm/vma.c:3203
> >  __do_sys_munmap mm/mmap.c:1077 [inline]
> >  __se_sys_munmap mm/mmap.c:1074 [inline]
> >  __x64_sys_munmap+0x60/0x70 mm/mmap.c:1074
> >  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> >  do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >
> > Memory state around the buggy address:
> >  ffff888052abdf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >  ffff888052abdf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > >ffff888052abe000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> >                    ^
> >  ffff888052abe080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> >  ffff888052abe100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > ==================================================================
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this issue. See:
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> >
> > If the report is already addressed, let syzbot know by replying with:
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> >
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> ---end quoted text---
>