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Subject[PATCH 5.4 020/309] netdevsim: fix stack-out-of-bounds in nsim_dev_debugfs_init()
Date
From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit 6fb8852b1298200da39bd85788bc5755d1d56f32 ]

When netdevsim dev is being created, a debugfs directory is created.
The variable "dev_ddir_name" is 16bytes device name pointer and device
name is "netdevsim<dev id>".
The maximum dev id length is 10.
So, 16bytes for device name isn't enough.

Test commands:
modprobe netdevsim
echo "1000000000 0" > /sys/bus/netdevsim/new_device

Splat looks like:
[ 249.622710][ T900] BUG: KASAN: stack-out-of-bounds in number+0x824/0x880
[ 249.623658][ T900] Write of size 1 at addr ffff88804c527988 by task bash/900
[ 249.624521][ T900]
[ 249.624830][ T900] CPU: 1 PID: 900 Comm: bash Not tainted 5.5.0+ #322
[ 249.625691][ T900] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 249.626712][ T900] Call Trace:
[ 249.627103][ T900] dump_stack+0x96/0xdb
[ 249.627639][ T900] ? number+0x824/0x880
[ 249.628173][ T900] print_address_description.constprop.5+0x1be/0x360
[ 249.629022][ T900] ? number+0x824/0x880
[ 249.629569][ T900] ? number+0x824/0x880
[ 249.630105][ T900] __kasan_report+0x12a/0x170
[ 249.630717][ T900] ? number+0x824/0x880
[ 249.631201][ T900] kasan_report+0xe/0x20
[ 249.631723][ T900] number+0x824/0x880
[ 249.632235][ T900] ? put_dec+0xa0/0xa0
[ 249.632716][ T900] ? rcu_read_lock_sched_held+0x90/0xc0
[ 249.633392][ T900] vsnprintf+0x63c/0x10b0
[ 249.633983][ T900] ? pointer+0x5b0/0x5b0
[ 249.634543][ T900] ? mark_lock+0x11d/0xc40
[ 249.635200][ T900] sprintf+0x9b/0xd0
[ 249.635750][ T900] ? scnprintf+0xe0/0xe0
[ 249.636370][ T900] nsim_dev_probe+0x63c/0xbf0 [netdevsim]
[ ... ]

Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Fixes: ab1d0cc004d7 ("netdevsim: change debugfs tree topology")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/netdevsim/dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -73,7 +73,7 @@ static const struct file_operations nsim

static int nsim_dev_debugfs_init(struct nsim_dev *nsim_dev)
{
- char dev_ddir_name[16];
+ char dev_ddir_name[sizeof(DRV_NAME) + 10];

sprintf(dev_ddir_name, DRV_NAME "%u", nsim_dev->nsim_bus_dev->dev.id);
nsim_dev->ddir = debugfs_create_dir(dev_ddir_name, nsim_dev_ddir);

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