CVE-2024-35949

Published May 20, 2024

Last updated 6 months ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: make sure that WRITTEN is set on all metadata blocks We previously would call btrfs_check_leaf() if we had the check integrity code enabled, which meant that we could only run the extended leaf checks if we had WRITTEN set on the header flags. This leaves a gap in our checking, because we could end up with corruption on disk where WRITTEN isn't set on the leaf, and then the extended leaf checks don't get run which we rely on to validate all of the item pointers to make sure we don't access memory outside of the extent buffer. However, since 732fab95abe2 ("btrfs: check-integrity: remove CONFIG_BTRFS_FS_CHECK_INTEGRITY option") we no longer call btrfs_check_leaf() from btrfs_mark_buffer_dirty(), which means we only ever call it on blocks that are being written out, and thus have WRITTEN set, or that are being read in, which should have WRITTEN set. Add checks to make sure we have WRITTEN set appropriately, and then make sure __btrfs_check_leaf() always does the item checking. This will protect us from file systems that have been corrupted and no longer have WRITTEN set on some of the blocks. This was hit on a crafted image tweaking the WRITTEN bit and reported by KASAN as out-of-bound access in the eb accessors. The example is a dir item at the end of an eb. [2.042] BTRFS warning (device loop1): bad eb member start: ptr 0x3fff start 30572544 member offset 16410 size 2 [2.040] general protection fault, probably for non-canonical address 0xe0009d1000000003: 0000 [#1] PREEMPT SMP KASAN NOPTI [2.537] KASAN: maybe wild-memory-access in range [0x0005088000000018-0x000508800000001f] [2.729] CPU: 0 PID: 2587 Comm: mount Not tainted 6.8.2 #1 [2.729] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 [2.621] RIP: 0010:btrfs_get_16+0x34b/0x6d0 [2.621] RSP: 0018:ffff88810871fab8 EFLAGS: 00000206 [2.621] RAX: 0000a11000000003 RBX: ffff888104ff8720 RCX: ffff88811b2288c0 [2.621] RDX: dffffc0000000000 RSI: ffffffff81dd8aca RDI: ffff88810871f748 [2.621] RBP: 000000000000401a R08: 0000000000000001 R09: ffffed10210e3ee9 [2.621] R10: ffff88810871f74f R11: 205d323430333737 R12: 000000000000001a [2.621] R13: 000508800000001a R14: 1ffff110210e3f5d R15: ffffffff850011e8 [2.621] FS: 00007f56ea275840(0000) GS:ffff88811b200000(0000) knlGS:0000000000000000 [2.621] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [2.621] CR2: 00007febd13b75c0 CR3: 000000010bb50000 CR4: 00000000000006f0 [2.621] Call Trace: [2.621] <TASK> [2.621] ? show_regs+0x74/0x80 [2.621] ? die_addr+0x46/0xc0 [2.621] ? exc_general_protection+0x161/0x2a0 [2.621] ? asm_exc_general_protection+0x26/0x30 [2.621] ? btrfs_get_16+0x33a/0x6d0 [2.621] ? btrfs_get_16+0x34b/0x6d0 [2.621] ? btrfs_get_16+0x33a/0x6d0 [2.621] ? __pfx_btrfs_get_16+0x10/0x10 [2.621] ? __pfx_mutex_unlock+0x10/0x10 [2.621] btrfs_match_dir_item_name+0x101/0x1a0 [2.621] btrfs_lookup_dir_item+0x1f3/0x280 [2.621] ? __pfx_btrfs_lookup_dir_item+0x10/0x10 [2.621] btrfs_get_tree+0xd25/0x1910 [ copy more details from report ]
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Analyzed
Products
linux_kernel, fedora

Risk scores

CVSS 3.1

Type
Primary
Base score
7.8
Impact score
5.9
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity
HIGH

Weaknesses

nvd@nist.gov
CWE-787

Social media

Hype score
Not currently trending

Configurations

  1. In the Linux kernel, the following vulnerability has been resolved: coresight: tmc-etr: Fix race condition between sysfs and perf mode When trying to run perf and sysfs mode simultaneously, the WARN_ON() in tmc_etr_enable_hw() is triggered sometimes: WARNING: CPU: 42 PID: 3911571 at drivers/hwtracing/coresight/coresight-tmc-etr.c:1060 tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] [..snip..] Call trace: tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] (P) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] (L) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] coresight_enable_path+0x1c8/0x218 [coresight] coresight_enable_sysfs+0xa4/0x228 [coresight] enable_source_store+0x58/0xa8 [coresight] dev_attr_store+0x20/0x40 sysfs_kf_write+0x4c/0x68 kernfs_fop_write_iter+0x120/0x1b8 vfs_write+0x2c8/0x388 ksys_write+0x74/0x108 __arm64_sys_write+0x24/0x38 el0_svc_common.constprop.0+0x64/0x148 do_el0_svc+0x24/0x38 el0_svc+0x3c/0x130 el0t_64_sync_handler+0xc8/0xd0 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Since the enablement of sysfs mode is separeted into two critical regions, one for sysfs buffer allocation and another for hardware enablement, it's possible to race with the perf mode. Fix this by double check whether the perf mode's been used before enabling the hardware in sysfs mode. mode: [sysfs mode] [perf mode] tmc_etr_get_sysfs_buffer() spin_lock(&drvdata->spinlock) [sysfs buffer allocation] spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() drvdata->etr_buf = etr_perf->etr_buf spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() WARN_ON(drvdata->etr_buf) // WARN sicne etr_buf initialized at the perf side spin_unlock(&drvdata->spinlock) With this fix, we retain the check for CS_MODE_PERF in get_etr_sysfs_buf. This ensures we verify whether the perf mode's already running before we actually allocate the buffer. Then we can save the time of allocating/freeing the sysfs buffer if race with the perf mode.CVE-2026-46272