CVE-2023-52701 — net: use a bounce buffer for copying skb->mark

Affected: Linux

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

net: use a bounce buffer for copying skb->mark

syzbot found arm64 builds would crash in sock_recv_mark() when CONFIG_HARDENED_USERCOPY=y

x86 and powerpc are not detecting the issue because they define user_access_begin. This will be handled in a different patch, because a check_object_size() is missing.

Only data from skb->cb[] can be copied directly to/from user space, as explained in commit 79a8a642bf05 ("net: Whitelist the skbuff_head_cache "cb" field")

syzbot report was: usercopy: Kernel memory exposure attempt detected from SLUB object 'skbuff_head_cache' (offset 168, size 4)! ------------[ cut here ]------------ kernel BUG at mm/usercopy.c:102 ! Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 4410 Comm: syz-executor533 Not tainted 6.2.0-rc7-syzkaller-17907-g2d3827b3f393 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : usercopy_abort+0x90/0x94 mm/usercopy.c:90 lr : usercopy_abort+0x90/0x94 mm/usercopy.c:90 sp : ffff80000fb9b9a0 x29: ffff80000fb9b9b0 x28: ffff0000c6073400 x27: 0000000020001a00 x26: 0000000000000014 x25: ffff80000cf52000 x24: fffffc0000000000 x23: 05ffc00000000200 x22: fffffc000324bf80 x21: ffff0000c92fe1a8 x20: 0000000000000001 x19: 0000000000000004 x18: 0000000000000000 x17: 656a626f2042554c x16: ffff0000c6073dd0 x15: ffff8000…

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CVE-2023-52701 — net: use a bounce buffer for copying skb->mark