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Hillf Danton authored
If a request_key authentication token key gets revoked, there's a window in which request_key_auth_describe() can see it with a NULL payload - but it makes no check for this and something like the following oops may occur: BUG: Kernel NULL pointer dereference at 0x00000038 Faulting instruction address: 0xc0000000004ddf30 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP [...] request_key_auth_describe+0x90/0xd0 LR [...] request_key_auth_describe+0x54/0xd0 Call Trace: [...] request_key_auth_describe+0x54/0xd0 (unreliable) [...] proc_keys_show+0x308/0x4c0 [...] seq_read+0x3d0/0x540 [...] proc_reg_read+0x90/0x110 [...] __vfs_read+0x3c/0x70 [...] vfs_read+0xb4/0x1b0 [...] ksys_read+0x7c/0x130 [...] system_call+0x5c/0x70 Fix this by checking for a NULL pointer when describing such a key. Also make the read routine check for a NULL pointer to be on the safe side. [DH: Modified to not take already-held rcu lock and modified to also check in the read routine] Fixes: 04c567d9 ("[PATCH] Keys: Fix race between two instantiators of a key") Reported-by:
Sachin Sant <sachinp@linux.vnet.ibm.com> Signed-off-by:
Hillf Danton <hdanton@sina.com> Signed-off-by:
David Howells <dhowells@redhat.com> Tested-by:
Sachin Sant <sachinp@linux.vnet.ibm.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
d41a3eff