CVE-2022-50214

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

coresight: Clear the connection field properly

coresight devices track their connections (output connections) and hold a reference to the fwnode. When a device goes away, we walk through the devices on the coresight bus and make sure that the references are dropped. This happens both ways: a) For all output connections from the device, drop the reference to the target device via coresightreleaseplatform_data()

b) Iterate over all the devices on the coresight bus and drop the reference to fwnode if this device is the target of the output connection, via coresightremoveconns()->coresightremovematch().

However, the coresightremovematch() doesn't clear the fwnode field, after dropping the reference, this causes use-after-free and additional refcount drops on the fwnode.

e.g., if we have two devices, A and B, with a connection, A -> B. If we remove B first, B would clear the reference on B, from A via coresightremovematch(). But when A is removed, it still has a connection with fwnode still pointing to B. Thus it tries to drops the reference in coresightreleaseplatform_data(), raising the bells like :

[ 91.990153] ------------[ cut here ]------------ [ 91.990163] refcountt: addition on 0; use-after-free. [ 91.990212] WARNING: CPU: 0 PID: 461 at lib/refcount.c:25 refcountwarnsaturate+0xa0/0x144 [ 91.990260] Modules linked in: coresightfunnel coresightreplicator coresightetm4x(-) crct10difce coresight iptables xtables ipv6 [last unloaded: coresightcpudebug] [ 91.990398] CPU: 0 PID: 461 Comm: rmmod Tainted: G W T 5.19.0-rc2+ #53 [ 91.990418] Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Feb 1 2019 [ 91.990434] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 91.990454] pc : refcountwarnsaturate+0xa0/0x144 [ 91.990476] lr : refcountwarnsaturate+0xa0/0x144 [ 91.990496] sp : ffff80000c843640 [ 91.990509] x29: ffff80000c843640 x28: ffff800009957c28 x27: ffff80000c8439a8 [ 91.990560] x26: ffff00097eff1990 x25: ffff8000092b6ad8 x24: ffff00097eff19a8 [ 91.990610] x23: ffff80000c8439a8 x22: 0000000000000000 x21: ffff80000c8439c2 [ 91.990659] x20: 0000000000000000 x19: ffff00097eff1a10 x18: ffff80000ab99c40 [ 91.990708] x17: 0000000000000000 x16: 0000000000000000 x15: ffff80000abf6fa0 [ 91.990756] x14: 000000000000001d x13: 0a2e656572662d72 x12: 657466612d657375 [ 91.990805] x11: 203b30206e6f206e x10: 6f69746964646120 x9 : ffff8000081aba28 [ 91.990854] x8 : 206e6f206e6f6974 x7 : 69646461203a745f x6 : 746e756f63666572 [ 91.990903] x5 : ffff00097648ec58 x4 : 0000000000000000 x3 : 0000000000000027 [ 91.990952] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff00080260ba00 [ 91.991000] Call trace: [ 91.991012] refcountwarnsaturate+0xa0/0x144 [ 91.991034] kobjectget+0xac/0xb0 [ 91.991055] ofnodeget+0x2c/0x40 [ 91.991076] offwnodeget+0x40/0x60 [ 91.991094] fwnodehandleget+0x3c/0x60 [ 91.991116] fwnodegetnthparent+0xf4/0x110 [ 91.991137] fwnodefullnamestring+0x48/0xc0 [ 91.991158] devicenodestring+0x41c/0x530 [ 91.991178] pointer+0x320/0x3ec [ 91.991198] vsnprintf+0x23c/0x750 [ 91.991217] vprintkstore+0x104/0x4b0 [ 91.991238] vprintkemit+0x8c/0x360 [ 91.991257] vprintkdefault+0x44/0x50 [ 91.991276] vprintk+0xcc/0xf0 [ 91.991295] _printk+0x68/0x90 [ 91.991315] ofnoderelease+0x13c/0x14c [ 91.991334] kobjectput+0x98/0x114 [ 91.991354] ofnodeput+0x24/0x34 [ 91.991372] offwnodeput+0x40/0x5c [ 91.991390] fwnodehandleput+0x38/0x50 [ 91.991411] coresightreleaseplatformdata+0x74/0xb0 [coresight] [ 91.991472] coresightunregister+0x64/0xcc [coresight] [ 91.991525] etm4removedev+0x64/0x78 [coresightetm4x] [ 91.991563] etm4removeamba+0x1c/0x2c [coresightetm4x] [ 91.991598] amba_remove+0x3c/0x19c ---truncated---