Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 13 Aug 2020 17:37:22 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH][v2] proc: use vmalloc for our kernel buffer |
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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@toxicpanda.com> > --- > 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?
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