### [CVE-2025-38260](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-38260)
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### Description

In the Linux kernel, the following vulnerability has been resolved:btrfs: handle csum tree error with rescue=ibadroots correctly[BUG]There is syzbot based reproducer that can crash the kernel, with thefollowing call trace: (With some debug output added) DEBUG: rescue=ibadroots parsed BTRFS: device fsid 14d642db-7b15-43e4-81e6-4b8fac6a25f8 devid 1 transid 8 /dev/loop0 (7:0) scanned by repro (1010) BTRFS info (device loop0): first mount of filesystem 14d642db-7b15-43e4-81e6-4b8fac6a25f8 BTRFS info (device loop0): using blake2b (blake2b-256-generic) checksum algorithm BTRFS info (device loop0): using free-space-tree BTRFS warning (device loop0): checksum verify failed on logical 5312512 mirror 1 wanted 0xb043382657aede36608fd3386d6b001692ff406164733d94e2d9a180412c6003 found 0x810ceb2bacb7f0f9eb2bf3b2b15c02af867cb35ad450898169f3b1f0bd818651 level 0 DEBUG: read tree root path failed for tree csum, ret=-5 BTRFS warning (device loop0): checksum verify failed on logical 5328896 mirror 1 wanted 0x51be4e8b303da58e6340226815b70e3a93592dac3f30dd510c7517454de8567a found 0x51be4e8b303da58e634022a315b70e3a93592dac3f30dd510c7517454de8567a level 0 BTRFS warning (device loop0): checksum verify failed on logical 5292032 mirror 1 wanted 0x1924ccd683be9efc2fa98582ef58760e3848e9043db8649ee382681e220cdee4 found 0x0cb6184f6e8799d9f8cb335dccd1d1832da1071d12290dab3b85b587ecacca6e level 0 process 'repro' launched './file2' with NULL argv: empty string added DEBUG: no csum root, idatacsums=0 ibadroots=134217728 Oops: general protection fault, probably for non-canonical address 0xdffffc0000000041: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000208-0x000000000000020f] CPU: 5 UID: 0 PID: 1010 Comm: repro Tainted: G           OE       6.15.0-custom+ #249 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 RIP: 0010:btrfs_lookup_csum+0x93/0x3d0 [btrfs] Call Trace:  <TASK>  btrfs_lookup_bio_sums+0x47a/0xdf0 [btrfs]  btrfs_submit_bbio+0x43e/0x1a80 [btrfs]  submit_one_bio+0xde/0x160 [btrfs]  btrfs_readahead+0x498/0x6a0 [btrfs]  read_pages+0x1c3/0xb20  page_cache_ra_order+0x4b5/0xc20  filemap_get_pages+0x2d3/0x19e0  filemap_read+0x314/0xde0  __kernel_read+0x35b/0x900  bprm_execve+0x62e/0x1140  do_execveat_common.isra.0+0x3fc/0x520  __x64_sys_execveat+0xdc/0x130  do_syscall_64+0x54/0x1d0  entry_SYSCALL_64_after_hwframe+0x76/0x7e ---[ end trace 0000000000000000 ]---[CAUSE]Firstly the fs has a corrupted csum tree root, thus to mount the fs wehave to go "ro,rescue=ibadroots" mount option.Normally with that mount option, a bad csum tree root should setBTRFS_FS_STATE_NO_DATA_CSUMS flag, so that any future data read willignore csum search.But in this particular case, we have the following call trace thatcaused NULL csum root, but not setting BTRFS_FS_STATE_NO_DATA_CSUMS:load_global_roots_objectid():		ret = btrfs_search_slot();		/* Succeeded */		btrfs_item_key_to_cpu()		found = true;		/* We found the root item for csum tree. */		root = read_tree_root_path();		if (IS_ERR(root)) {			if (!btrfs_test_opt(fs_info, IGNOREBADROOTS))			/*			 * Since we have rescue=ibadroots mount option,			 * @ret is still 0.			 */			break;	if (!found || ret) {		/* @found is true, @ret is 0, error handling for csum		 * tree is skipped.		 */	}This means we completely skipped to set BTRFS_FS_STATE_NO_DATA_CSUMS ifthe csum tree is corrupted, which results unexpected later csum lookup.[FIX]If read_tree_root_path() failed, always populate @ret to the errornumber.As at the end of the function, we need @ret to determine if we need todo the extra error handling for csum tree.

### POC

#### Reference
No PoCs from references.

#### Github
- https://github.com/w4zu/Debian_security