From: Kees Cook <keescook@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Michal Hocko <mhocko@suse.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Lee Duncan <lduncan@suse.com>, Chris Leech <cleech@redhat.com>,
Adam Nichols <adam@grimm-co.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: [PATCH] seq_file: Unconditionally use vmalloc for buffer
Date: Fri, 12 Mar 2021 12:55:58 -0800 [thread overview]
Message-ID: <20210312205558.2947488-1-keescook@chromium.org> (raw)
The sysfs interface to seq_file continues to be rather fragile, as seen
with some recent exploits[1]. Move the seq_file buffer to the vmap area
(while retaining the accounting flag), since it has guard pages that
will catch and stop linear overflows. This seems justified given that
seq_file already uses kvmalloc(), that allocations are normally short
lived, and that they are not normally performance critical.
[1] https://blog.grimm-co.com/2021/03/new-old-bugs-in-linux-kernel.html
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/seq_file.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/fs/seq_file.c b/fs/seq_file.c
index cb11a34fb871..ad78577d4c2c 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -32,7 +32,7 @@ static void seq_set_overflow(struct seq_file *m)
static void *seq_buf_alloc(unsigned long size)
{
- return kvmalloc(size, GFP_KERNEL_ACCOUNT);
+ return __vmalloc(size, GFP_KERNEL_ACCOUNT);
}
/**
@@ -130,7 +130,7 @@ static int traverse(struct seq_file *m, loff_t offset)
Eoverflow:
m->op->stop(m, p);
- kvfree(m->buf);
+ vfree(m->buf);
m->count = 0;
m->buf = seq_buf_alloc(m->size <<= 1);
return !m->buf ? -ENOMEM : -EAGAIN;
@@ -237,7 +237,7 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
goto Fill;
// need a bigger buffer
m->op->stop(m, p);
- kvfree(m->buf);
+ vfree(m->buf);
m->count = 0;
m->buf = seq_buf_alloc(m->size <<= 1);
if (!m->buf)
@@ -349,7 +349,7 @@ EXPORT_SYMBOL(seq_lseek);
int seq_release(struct inode *inode, struct file *file)
{
struct seq_file *m = file->private_data;
- kvfree(m->buf);
+ vfree(m->buf);
kmem_cache_free(seq_file_cache, m);
return 0;
}
@@ -585,7 +585,7 @@ int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
return -ENOMEM;
ret = single_open(file, show, data);
if (ret) {
- kvfree(buf);
+ vfree(buf);
return ret;
}
((struct seq_file *)file->private_data)->buf = buf;
--
2.25.1
next reply other threads:[~2021-03-12 20:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 20:55 Kees Cook [this message]
2021-03-13 8:54 ` [PATCH] seq_file: Unconditionally use vmalloc for buffer Greg Kroah-Hartman
2021-03-15 8:34 ` Michal Hocko
2021-03-15 17:40 ` Kees Cook
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