path: root/security/keys
diff options
authorHillf Danton <>2019-09-02 13:37:29 +0100
committerLinus Torvalds <>2019-09-05 14:19:25 -0700
commitd41a3effbb53b1bcea41e328d16a4d046a508381 (patch)
treead0fe28a37d6613b1d1b85e26b9cbf2b14963f60 /security/keys
parenta3f5e1f5783974813b5d43beb38c4eeaa67afbef (diff)
keys: Fix missing null pointer check in request_key_auth_describe()
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 <> Signed-off-by: Hillf Danton <> Signed-off-by: David Howells <> Tested-by: Sachin Sant <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'security/keys')
1 files changed, 6 insertions, 0 deletions
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index e73ec040e250..ecba39c93fd9 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -66,6 +66,9 @@ static void request_key_auth_describe(const struct key *key,
struct request_key_auth *rka = dereference_key_rcu(key);
+ if (!rka)
+ return;
seq_puts(m, "key:");
seq_puts(m, key->description);
if (key_is_positive(key))
@@ -83,6 +86,9 @@ 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;