CVE-2024-26870

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

NFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102

A call to listxattr() with a buffer size = 0 returns the actual size of the buffer needed for a subsequent call. When size > 0, nfs4_listxattr() does not return an error because either generic_listxattr() or nfs4_listxattr_nfs4_label() consumes exactly all the bytes then size is 0 when calling nfs4_listxattr_nfs4_user() which then triggers the following kernel BUG:

[ 99.403778] kernel BUG at mm/usercopy.c:102! [ 99.404063] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 99.408463] CPU: 0 PID: 3310 Comm: python3 Not tainted 6.6.0-61.fc40.aarch64 #1 [ 99.415827] Call trace: [ 99.415985] usercopy_abort+0x70/0xa0 [ 99.416227] __check_heap_object+0x134/0x158 [ 99.416505] check_heap_object+0x150/0x188 [ 99.416696] __check_object_size.part.0+0x78/0x168 [ 99.416886] __check_object_size+0x28/0x40 [ 99.417078] listxattr+0x8c/0x120 [ 99.417252] path_listxattr+0x78/0xe0 [ 99.417476] __arm64_sys_listxattr+0x28/0x40 [ 99.417723] invoke_syscall+0x78/0x100 [ 99.417929] el0_svc_common.constprop.0+0x48/0xf0 [ 99.418186] do_el0_svc+0x24/0x38 [ 99.418376] el0_svc+0x3c/0x110 [ 99.418554] el0t_64_sync_handler+0x120/0x130 [ 99.418788] el0t_64_sync+0x194/0x198 [ 99.418994] Code: aa0003e3 d000a3e0 91310000 97f49bdb (d4210000)

Issue is reproduced when generic_listxattr() returns system.nfs4_acl, thus calling lisxattr() with size = 16 will trigger the bug.

Add check on nfs4_listxattr() to return ERANGE error when it is called with size > 0 and the return value is greater than size.

Affected Software

References

• https://git.kernel.org/stable/c/06e828b3f1b206de08ef520fc46a40b22e1869cb
• https://git.kernel.org/stable/c/23bfecb4d852751d5e403557dd500bb563313baf
• https://git.kernel.org/stable/c/251a658bbfceafb4d58c76b77682c8bf7bcfad65
• https://git.kernel.org/stable/c/4403438eaca6e91f02d272211c4d6b045092396b
• https://git.kernel.org/stable/c/79cdcc765969d23f4e3d6ea115660c3333498768
• https://git.kernel.org/stable/c/80365c9f96015bbf048fdd6c8705d3f8770132bf
• https://git.kernel.org/stable/c/9d52865ff28245fc2134da9f99baff603a24407a