On 8/13/20 11:37 AM, Christoph Hellwig wrote:
On Thu, Aug 13, 2020 at 11:33:56AM -0400, Josef Bacik wrote:
Since
sysctl: pass kernel pointers to ->proc_handler
we have been pre-allocating a buffer to copy the data from the proc
handlers into, and then copying that to userspace. The problem is this
just blind kmalloc()'s the buffer size passed in from the read, which in
the case of our 'cat' binary was 64kib. Order-4 allocations are not
awesome, and since we can potentially allocate up to our maximum order,
use vmalloc for these buffers.
Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
v1->v2:
- Make vmemdup_user_nul actually do the right thing...sorry about that.
fs/proc/proc_sysctl.c | 6 +++---
include/linux/string.h | 1 +
mm/util.c | 27 +++++++++++++++++++++++++++
3 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 6c1166ccdaea..207ac6e6e028 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -571,13 +571,13 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
goto out;
if (write) {
- kbuf = memdup_user_nul(ubuf, count);
+ kbuf = vmemdup_user_nul(ubuf, count);
Given that this can also do a kmalloc and thus needs to be paired
with kvfree shouldn't it be kvmemdup_user_nul?
There's an existing vmemdup_user that does kvmalloc, so I followed the existing
naming convention. Do you want me to change them both? Thanks,
Josef
