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ebiggersJames Morris
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James Morris
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KEYS: fix dereferencing NULL payload with nonzero length
sys_add_key() and the KEYCTL_UPDATE operation of sys_keyctl() allowed a NULL payload with nonzero length to be passed to the key type's ->preparse(), ->instantiate(), and/or ->update() methods. Various key types including asymmetric, cifs.idmap, cifs.spnego, and pkcs7_test did not handle this case, allowing an unprivileged user to trivially cause a NULL pointer dereference (kernel oops) if one of these key types was present. Fix it by doing the copy_from_user() when 'plen' is nonzero rather than when '_payload' is non-NULL, causing the syscall to fail with EFAULT as expected when an invalid buffer is specified. Cc: stable@vger.kernel.org # 2.6.10+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
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Diff for: security/keys/keyctl.c

+2-2
Original file line numberDiff line numberDiff line change
@@ -99,7 +99,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
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/* pull the payload in if one was supplied */
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payload = NULL;
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102-
if (_payload) {
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if (plen) {
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ret = -ENOMEM;
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payload = kvmalloc(plen, GFP_KERNEL);
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if (!payload)
@@ -324,7 +324,7 @@ long keyctl_update_key(key_serial_t id,
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/* pull the payload in if one was supplied */
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payload = NULL;
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if (_payload) {
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if (plen) {
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ret = -ENOMEM;
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payload = kmalloc(plen, GFP_KERNEL);
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if (!payload)

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