From: Josef Bacik <josef@xxxxxxxxxxxxxx> Subject: proc: use kvzalloc for our kernel buffer 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 blindly kzalloc()'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, so use kvzalloc for these buffers. [willy@xxxxxxxxxxxxx: changelog tweaks] Link: https://lkml.kernel.org/r/6345270a2c1160b89dd5e6715461f388176899d1.1612972413.git.josef@xxxxxxxxxxxxxx Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler") Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx> CC: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/proc_sysctl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/fs/proc/proc_sysctl.c~proc-use-vmalloc-for-our-kernel-buffer +++ a/fs/proc/proc_sysctl.c @@ -571,7 +571,7 @@ static ssize_t proc_sys_call_handler(str error = -ENOMEM; if (count >= KMALLOC_MAX_SIZE) goto out; - kbuf = kzalloc(count + 1, GFP_KERNEL); + kbuf = kvzalloc(count + 1, GFP_KERNEL); if (!kbuf) goto out; @@ -600,7 +600,7 @@ static ssize_t proc_sys_call_handler(str error = count; out_free_buf: - kfree(kbuf); + kvfree(kbuf); out: sysctl_head_finish(head); _
