CVE-2024-38599

In the Linux kernel, the following vulnerability has been resolved:

jffs2: prevent xattr node from overflowing the eraseblock

Add a check to make sure that the requested xattr node size is no larger

than the eraseblock minus the cleanmarker.

Unlike the usual inode nodes, the xattr nodes aren't split into parts

and spread across multiple eraseblocks, which means that a xattr node

must not occupy more than one eraseblock. If the requested xattr value is

too large, the xattr node can spill onto the next eraseblock, overwriting

the nodes and causing errors such as:

jffs2: argh. node added in wrong place at 0x0000b050(2)

jffs2: nextblock 0x0000a000, expected at 0000b00c

jffs2: error: (823) do_verify_xattr_datum: node CRC failed at 0x01e050,

read=0xfc892c93, calc=0x000000

jffs2: notice: (823) jffs2_get_inode_nodes: Node header CRC failed

at 0x01e00c. {848f,2fc4,0fef511f,59a3d171}

jffs2: Node at 0x0000000c with length 0x00001044 would run over the

end of the erase block

jffs2: Perhaps the file system was created with the wrong erase size?

jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found

at 0x00000010: 0x1044 instead

This breaks the filesystem and can lead to KASAN crashes such as:

BUG: KASAN: slab-out-of-bounds in jffs2_sum_add_kvec+0x125e/0x15d0

Read of size 4 at addr ffff88802c31e914 by task repro/830

CPU: 0 PID: 830 Comm: repro Not tainted 6.9.0-rc3+ #1

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),

BIOS Arch Linux 1.16.3-1-1 04/01/2014

Call Trace:

<TASK>

dump_stack_lvl+0xc6/0x120

print_report+0xc4/0x620

? __virt_addr_valid+0x308/0x5b0

kasan_report+0xc1/0xf0

? jffs2_sum_add_kvec+0x125e/0x15d0

? jffs2_sum_add_kvec+0x125e/0x15d0

jffs2_sum_add_kvec+0x125e/0x15d0

jffs2_flash_direct_writev+0xa8/0xd0

jffs2_flash_writev+0x9c9/0xef0

? __x64_sys_setxattr+0xc4/0x160

? do_syscall_64+0x69/0x140

? entry_SYSCALL_64_after_hwframe+0x76/0x7e

[...]

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.