From: Hillf Danton hdanton@sina.com
[ Upstream commit d41a3effbb53b1bcea41e328d16a4d046a508381 ]
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: 04c567d9313e ("[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 Signed-off-by: Sasha Levin sashal@kernel.org --- security/keys/request_key_auth.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index 8882b729924dd..976deea0569e3 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -71,6 +71,9 @@ static void request_key_auth_describe(const struct key *key, { struct request_key_auth *rka = key->payload.data[0];
+ if (!rka) + return; + seq_puts(m, "key:"); seq_puts(m, key->description); if (key_is_positive(key)) @@ -88,6 +91,9 @@ static long request_key_auth_read(const struct key *key, size_t datalen; long ret;
+ if (!rka) + return -EKEYREVOKED; + datalen = rka->callout_len; ret = datalen;