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| author | Hillf Danton <hdanton@sina.com> | 2019-09-02 13:37:29 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-05 14:19:25 -0700 |
| commit | d41a3effbb53b1bcea41e328d16a4d046a508381 (patch) | |
| tree | ad0fe28a37d6613b1d1b85e26b9cbf2b14963f60 /security/keys | |
| parent | a3f5e1f5783974813b5d43beb38c4eeaa67afbef (diff) | |
| download | linux-d41a3effbb53b1bcea41e328d16a4d046a508381.tar.gz linux-d41a3effbb53b1bcea41e328d16a4d046a508381.tar.bz2 linux-d41a3effbb53b1bcea41e328d16a4d046a508381.zip | |
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 <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>
Diffstat (limited to 'security/keys')
| -rw-r--r-- | security/keys/request_key_auth.c | 6 |
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; |