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.