two more fixes for sysctl

two more fixes for sysctl

[Christoph Hellwig]

Hi Al,

two more fixes for the kernel pointers in the sysctl handlers.

[PATCH 1/2] cdrom: fix an incorrect __user annotation on cdrom_sysctl_info

[Christoph Hellwig]

No user pointers for sysctls anymore.

Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Reported-by: build test robot <lkp@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/cdrom/cdrom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index e3bbe108eb542f..410060812e9dbf 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -3518,7 +3518,7 @@ static int cdrom_print_info(const char *header, int val, char *info,
 }
 
 static int cdrom_sysctl_info(struct ctl_table *ctl, int write,
-                           void __user *buffer, size_t *lenp, loff_t *ppos)
+                           void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int pos;
 	char *info = cdrom_sysctl_settings.info;
-- 
2.26.2

[PATCH 2/2] sysctl: reject gigantic reads/write to sysctl files

[Christoph Hellwig]

Instead of triggering a WARN_ON deep down in the page allocator just
give up early on allocations that are way larger than the usual sysctl
values.

Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/proc/proc_sysctl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index df2143e05c571e..08c33bd1642dcd 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -564,6 +564,10 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
 	if (!table->proc_handler)
 		goto out;
 
+	/* don't even try if the size is too large */
+	if (count > KMALLOC_MAX_SIZE)
+		return -ENOMEM;
+
 	if (write) {
 		kbuf = memdup_user_nul(ubuf, count);
 		if (IS_ERR(kbuf)) {
-- 
2.26.2

Re: two more fixes for sysctl

[Luis Chamberlain]

On Tue, Jun 09, 2020 at 07:08:17PM +0200, Christoph Hellwig wrote:
> Hi Al,
> 
> two more fixes for the kernel pointers in the sysctl handlers.

Acked-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis

Re: two more fixes for sysctl

[Al Viro]

On Tue, Jun 09, 2020 at 07:08:17PM +0200, Christoph Hellwig wrote:
> Hi Al,
> 
> two more fixes for the kernel pointers in the sysctl handlers.

Applied and pushed.  Let me beat it up a bit, if it survives - to
Linus it goes...