[PATCH] KEYS: fix writing past end of user-supplied buffer in keyring_read()
From: Eric Biggers <hidden>
Date: 2017-09-18 18:36:59
Also in:
keyrings, lkml, stable
Subsystem:
keys/keyrings, security subsystem, the rest · Maintainers:
David Howells, Jarkko Sakkinen, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
From: Eric Biggers <redacted>
Userspace can call keyctl_read() on a keyring to get the list of IDs of
keys in the keyring. But if the user-supplied buffer is too small, the
kernel would write the full list anyway --- which will corrupt whatever
userspace memory happened to be past the end of the buffer. Fix it by
only filling the space that is available.
Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring")
Cc: <redacted> [v3.13+]
Signed-off-by: Eric Biggers <redacted>
---
security/keys/keyring.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index d8d08bd9c159..4fa82a8a9c0e 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c@@ -423,7 +423,7 @@ static void keyring_describe(const struct key *keyring, struct seq_file *m) } struct keyring_read_iterator_context { - size_t qty; + size_t buflen; size_t count; key_serial_t __user *buffer; };
@@ -435,9 +435,9 @@ static int keyring_read_iterator(const void *object, void *data) int ret; kenter("{%s,%d},,{%zu/%zu}", - key->type->name, key->serial, ctx->count, ctx->qty); + key->type->name, key->serial, ctx->count, ctx->buflen); - if (ctx->count >= ctx->qty) + if (ctx->count >= ctx->buflen) return 1; ret = put_user(key->serial, ctx->buffer);
@@ -472,16 +472,12 @@ static long keyring_read(const struct key *keyring, return 0; /* Calculate how much data we could return */ - ctx.qty = nr_keys * sizeof(key_serial_t); - if (!buffer || !buflen) - return ctx.qty; - - if (buflen > ctx.qty) - ctx.qty = buflen; + return nr_keys * sizeof(key_serial_t); /* Copy the IDs of the subscribed keys into the buffer */ ctx.buffer = (key_serial_t __user *)buffer; + ctx.buflen = buflen; ctx.count = 0; ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx); if (ret < 0) {
--
2.14.1.690.gbb1197296e-goog
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