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authorHillf Danton <hdanton@sina.com>2019-09-02 13:37:29 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-09-21 07:14:21 +0200
commitb94178b239d797c204b045c6a0b77c43cbe82f8f (patch)
treefbbbb0d9459f8465e81382337c28872b75aa1cf9
parent06961928f5f37dcf0fac563ffde2916d390bd22c (diff)
keys: Fix missing null pointer check in request_key_auth_describe()
[ 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>
-rw-r--r--security/keys/request_key_auth.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index f60baeb338e5..b47445022d5c 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;