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authorMichael Ellerman <mpe@ellerman.id.au>2018-10-19 15:21:08 +1100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-02-20 10:13:12 +0100
commitcc980857718f2dd1edc385fade160b21f7770816 (patch)
tree420f42aff5144ed2bfbd9e8516010c3a21dd8ac5 /lib
parent90beb6bbed6719bf5ee73dadebe6fd99cb57cc98 (diff)
seq_buf: Make seq_buf_puts() null-terminate the buffer
[ Upstream commit 0464ed24380905d640030d368cd84a4e4d1e15e2 ] Currently seq_buf_puts() will happily create a non null-terminated string for you in the buffer. This is particularly dangerous if the buffer is on the stack. For example: char buf[8]; char secret = "secret"; struct seq_buf s; seq_buf_init(&s, buf, sizeof(buf)); seq_buf_puts(&s, "foo"); printk("Message is %s\n", buf); Can result in: Message is fooªªªªªsecret We could require all users to memset() their buffer to zero before use. But that seems likely to be forgotten and lead to bugs. Instead we can change seq_buf_puts() to always leave the buffer in a null-terminated state. The only downside is that this makes the buffer 1 character smaller for seq_buf_puts(), but that seems like a good trade off. Link: http://lkml.kernel.org/r/20181019042109.8064-1-mpe@ellerman.id.au Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/seq_buf.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 5c94e1012a91..cbef5ee4c459 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -143,9 +143,13 @@ int seq_buf_puts(struct seq_buf *s, const char *str)
WARN_ON(s->size == 0);
+ /* Add 1 to len for the trailing null byte which must be there */
+ len += 1;
+
if (seq_buf_can_fit(s, len)) {
memcpy(s->buffer + s->len, str, len);
- s->len += len;
+ /* Don't count the trailing null byte against the capacity */
+ s->len += len - 1;
return 0;
}
seq_buf_set_overflow(s);