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proc: use kvzalloc for our kernel buffer

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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@infradead.org: changelog tweaks]

Link: https://lkml.kernel.org/r/6345270a2c1160b89dd5e6715461f388176899d1.1612972413.git.josef@toxicpanda.com
Fixes: 32927393dc ("sysctl: pass kernel pointers to ->proc_handler")
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
CC: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Josef Bacik 2021-02-25 17:20:49 -08:00 committed by Linus Torvalds
parent 152c432b12
commit 4508943794
1 changed files with 2 additions and 2 deletions
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4
fs/proc/proc_sysctl.c
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@ -571,7 +571,7 @@ static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
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(struct kiocb *iocb, struct iov_iter *iter,
error = count;
out_free_buf:
kfree(kbuf);
kvfree(kbuf);
out:
sysctl_head_finish(head);