[syzbot] [ext4?] KASAN: use-after-free Read in ext4_search_dir (2)

[syzbot] [ext4?] KASAN: use-after-free Read in ext4_search_dir (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    47ac09b91bef Linux 6.11-rc4
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=153eeafd980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=0c2508114d912a54ee79
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=1335fe05980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156ba6fd980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-47ac09b9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6db2a1c6b666/vmlinux-47ac09b9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b1c782255526/bzImage-47ac09b9.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/83fcfca5f30f/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0c2508114d912a54ee79@syzkaller.appspotmail.com

EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
loop0: detected capacity change from 2048 to 2047
==================================================================
BUG: KASAN: use-after-free in ext4_search_dir+0xf2/0x1c0 fs/ext4/namei.c:1500
Read of size 1 at addr ffff88803e91130f by task syz-executor269/5103

CPU: 0 UID: 0 PID: 5103 Comm: syz-executor269 Not tainted 6.11.0-rc4-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 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
 ext4_search_dir+0xf2/0x1c0 fs/ext4/namei.c:1500
 ext4_find_inline_entry+0x4be/0x5e0 fs/ext4/inline.c:1697
 __ext4_find_entry+0x2b4/0x1b30 fs/ext4/namei.c:1573
 ext4_lookup_entry fs/ext4/namei.c:1727 [inline]
 ext4_lookup+0x15f/0x750 fs/ext4/namei.c:1795
 lookup_one_qstr_excl+0x11f/0x260 fs/namei.c:1633
 filename_create+0x297/0x540 fs/namei.c:3980
 do_symlinkat+0xf9/0x3a0 fs/namei.c:4587
 __do_sys_symlinkat fs/namei.c:4610 [inline]
 __se_sys_symlinkat fs/namei.c:4607 [inline]
 __x64_sys_symlinkat+0x95/0xb0 fs/namei.c:4607
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3e73ced469
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 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:00007fff4d40c258 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 0032656c69662f2e RCX: 00007f3e73ced469
RDX: 0000000020000200 RSI: 00000000ffffff9c RDI: 00000000200001c0
RBP: 0000000000000000 R08: 00007fff4d40c290 R09: 00007fff4d40c290
R10: 0023706f6f6c2f76 R11: 0000000000000246 R12: 00007fff4d40c27c
R13: 0000000000000003 R14: 431bde82d7b634db R15: 00007fff4d40c2b0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb7091d9 pfn:0x3e911
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000007fb7091d9 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_COMP|__GFP_ZERO), pid 5083, tgid 5083 (sshd), ts 84338308196, free_ts 84419190442
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493
 prep_new_page mm/page_alloc.c:1501 [inline]
 get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3439
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4695
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2263
 folio_alloc_mpol_noprof mm/mempolicy.c:2281 [inline]
 vma_alloc_folio_noprof+0x12e/0x230 mm/mempolicy.c:2312
 folio_prealloc+0x31/0x170
 alloc_anon_folio mm/memory.c:4498 [inline]
 do_anonymous_page mm/memory.c:4555 [inline]
 do_pte_missing mm/memory.c:3945 [inline]
 handle_pte_fault+0x255e/0x6fc0 mm/memory.c:5521
 __handle_mm_fault mm/memory.c:5664 [inline]
 handle_mm_fault+0x1029/0x1980 mm/memory.c:5832
 do_user_addr_fault arch/x86/mm/fault.c:1338 [inline]
 handle_page_fault arch/x86/mm/fault.c:1481 [inline]
 exc_page_fault+0x459/0x8c0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5083 tgid 5083 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1094 [inline]
 free_unref_folios+0x103a/0x1b00 mm/page_alloc.c:2660
 folios_put_refs+0x76e/0x860 mm/swap.c:1039
 free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:332
 __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:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:465
 unmap_region+0x2df/0x350 mm/mmap.c:2441
 do_vmi_align_munmap+0x1122/0x18c0 mm/mmap.c:2754
 do_vmi_munmap+0x261/0x2f0 mm/mmap.c:2830
 __vm_munmap+0x1fc/0x400 mm/mmap.c:3109
 __do_sys_munmap mm/mmap.c:3126 [inline]
 __se_sys_munmap mm/mmap.c:3123 [inline]
 __x64_sys_munmap+0x68/0x80 mm/mmap.c:3123
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803e911200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803e911280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88803e911300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88803e911380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803e911400: 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.
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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
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#syz undup

Re: [syzbot] [ext4?] KASAN: use-after-free Read in ext4_search_dir (2)

[Thadeu Lima de Souza Cascardo]

#syz test: upstream 47ac09b91befbb6a235ab620c32af719f8208399


diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index e7a09a99837b..44a5f6df59ec 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -1664,24 +1664,36 @@ struct buffer_head *ext4_find_inline_entry(struct inode *dir,
 					struct ext4_dir_entry_2 **res_dir,
 					int *has_inline_data)
 {
+	struct ext4_xattr_ibody_find is = {
+		.s = { .not_found = -ENODATA, },
+	};
+	struct ext4_xattr_info i = {
+		.name_index = EXT4_XATTR_INDEX_SYSTEM,
+		.name = EXT4_XATTR_SYSTEM_DATA,
+	};
 	int ret;
-	struct ext4_iloc iloc;
 	void *inline_start;
 	int inline_size;
 
-	if (ext4_get_inode_loc(dir, &iloc))
-		return NULL;
+	ret = ext4_get_inode_loc(dir, &is.iloc);
+	if (ret)
+		return ERR_PTR(ret);
 
 	down_read(&EXT4_I(dir)->xattr_sem);
+
+	ret = ext4_xattr_ibody_find(dir, &i, &is);
+	if (ret)
+		goto out;
+
 	if (!ext4_has_inline_data(dir)) {
 		*has_inline_data = 0;
 		goto out;
 	}
 
-	inline_start = (void *)ext4_raw_inode(&iloc)->i_block +
+	inline_start = (void *)ext4_raw_inode(&is.iloc)->i_block +
 						EXT4_INLINE_DOTDOT_SIZE;
 	inline_size = EXT4_MIN_INLINE_DATA_SIZE - EXT4_INLINE_DOTDOT_SIZE;
-	ret = ext4_search_dir(iloc.bh, inline_start, inline_size,
+	ret = ext4_search_dir(is.iloc.bh, inline_start, inline_size,
 			      dir, fname, 0, res_dir);
 	if (ret == 1)
 		goto out_find;
@@ -1691,20 +1703,23 @@ struct buffer_head *ext4_find_inline_entry(struct inode *dir,
 	if (ext4_get_inline_size(dir) == EXT4_MIN_INLINE_DATA_SIZE)
 		goto out;
 
-	inline_start = ext4_get_inline_xattr_pos(dir, &iloc);
+	inline_start = ext4_get_inline_xattr_pos(dir, &is.iloc);
 	inline_size = ext4_get_inline_size(dir) - EXT4_MIN_INLINE_DATA_SIZE;
 
-	ret = ext4_search_dir(iloc.bh, inline_start, inline_size,
+	ret = ext4_search_dir(is.iloc.bh, inline_start, inline_size,
 			      dir, fname, 0, res_dir);
 	if (ret == 1)
 		goto out_find;
 
 out:
-	brelse(iloc.bh);
-	iloc.bh = NULL;
+	brelse(is.iloc.bh);
+	if (ret < 0)
+		is.iloc.bh = ERR_PTR(ret);
+	else
+		is.iloc.bh = NULL;
 out_find:
 	up_read(&EXT4_I(dir)->xattr_sem);
-	return iloc.bh;
+	return is.iloc.bh;
 }
 
 int ext4_delete_inline_entry(handle_t *handle,
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 6a95713f9193..14163b32eddb 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1482,7 +1482,7 @@ static bool ext4_match(struct inode *parent,
 }
 
 /*
- * Returns 0 if not found, -1 on failure, and 1 on success
+ * Returns 0 if not found, -EFSCORRUPTED on failure, and 1 on success
  */
 int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 		    struct inode *dir, struct ext4_filename *fname,
@@ -1503,7 +1503,7 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 			 * a full check */
 			if (ext4_check_dir_entry(dir, NULL, de, bh, search_buf,
 						 buf_size, offset))
-				return -1;
+				return -EFSCORRUPTED;
 			*res_dir = de;
 			return 1;
 		}
@@ -1511,7 +1511,7 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 		de_len = ext4_rec_len_from_disk(de->rec_len,
 						dir->i_sb->s_blocksize);
 		if (de_len <= 0)
-			return -1;
+			return -EFSCORRUPTED;
 		offset += de_len;
 		de = (struct ext4_dir_entry_2 *) ((char *) de + de_len);
 	}
@@ -1574,7 +1574,7 @@ static struct buffer_head *__ext4_find_entry(struct inode *dir,
 					     &has_inline_data);
 		if (inlined)
 			*inlined = has_inline_data;
-		if (has_inline_data)
+		if (has_inline_data || IS_ERR(ret))
 			goto cleanup_and_exit;
 	}
 
@@ -1663,8 +1663,10 @@ static struct buffer_head *__ext4_find_entry(struct inode *dir,
 			goto cleanup_and_exit;
 		} else {
 			brelse(bh);
-			if (i < 0)
+			if (i < 0) {
+				ret = ERR_PTR(i);
 				goto cleanup_and_exit;
+			}
 		}
 	next:
 		if (++block >= nblocks)
@@ -1758,7 +1760,7 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
 		if (retval == 1)
 			goto success;
 		brelse(bh);
-		if (retval == -1) {
+		if (retval < 0) {
 			bh = ERR_PTR(ERR_BAD_DX_DIR);
 			goto errout;
 		}

Re: [syzbot] [ext4?] KASAN: use-after-free Read in ext4_search_dir (2)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+0c2508114d912a54ee79@syzkaller.appspotmail.com
Tested-by: syzbot+0c2508114d912a54ee79@syzkaller.appspotmail.com

Tested on:

commit:         47ac09b9 Linux 6.11-rc4
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10631a91980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=0c2508114d912a54ee79
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=163ed3f5980000

Note: testing is done by a robot and is best-effort only.