Re: [PATCH] kgdboc: Passing ekgdboc to command line causes panic
From: Daniel Thompson <hidden>
Date: 2018-08-14 09:16:08
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On Wed, Aug 08, 2018 at 11:59:44PM +0800, zhe.he@windriver.com wrote:
From: He Zhe <redacted> kgdboc_option_setup does not check input argument before passing it to strlen. The argument would be a NULL pointer if "ekgdboc", without its value, is set in command line and thus cause the following panic. PANIC: early exception 0xe3 IP 10:ffffffff8fbbb620 error 0 cr2 0x0 [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18-rc8+ #1 [ 0.000000] RIP: 0010:strlen+0x0/0x20 ... [ 0.000000] Call Trace [ 0.000000] ? kgdboc_option_setup+0x9/0xa0 [ 0.000000] ? kgdboc_early_init+0x6/0x1b [ 0.000000] ? do_early_param+0x4d/0x82 [ 0.000000] ? parse_args+0x212/0x330 [ 0.000000] ? rdinit_setup+0x26/0x26 [ 0.000000] ? parse_early_options+0x20/0x23 [ 0.000000] ? rdinit_setup+0x26/0x26 [ 0.000000] ? parse_early_param+0x2d/0x39 [ 0.000000] ? setup_arch+0x2f7/0xbf4 [ 0.000000] ? start_kernel+0x5e/0x4c2 [ 0.000000] ? load_ucode_bsp+0x113/0x12f [ 0.000000] ? secondary_startup_64+0xa5/0xb0 This patch adds a check to prevent the panic and changes some printk to right fashion. Signed-off-by: He Zhe <redacted>
For the bug fix portions of this patch you should add the stable kernel ML to the Cc: of the sign off area: See: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1
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--- drivers/tty/serial/kgdboc.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index b4ba2b1..0003d6c 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c@@ -130,8 +130,13 @@ static void kgdboc_unregister_kbd(void) static int kgdboc_option_setup(char *opt) { + if (!opt) { + pr_err("kgdboc: null option\n"); + return -EINVAL; + } + if (strlen(opt) >= MAX_CONFIG_LEN) { - printk(KERN_ERR "kgdboc: config string too long\n"); + pr_err("kgdboc: config string too long\n");
These changes are not bug fixes and are not normally candidates for backporting. It would therefore be better to put the s/printk KERN_ERR /pr_err(/ changes into a separate patch.
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return -ENOSPC; } strcpy(config, opt);@@ -248,7 +253,7 @@ static int param_set_kgdboc_var(const char *kmessage, int len = strlen(kmessage); if (len >= MAX_CONFIG_LEN) { - printk(KERN_ERR "kgdboc: config string too long\n"); + pr_err("kgdboc: config string too long\n"); return -ENOSPC; }@@ -259,8 +264,7 @@ static int param_set_kgdboc_var(const char *kmessage, } if (kgdb_connected) { - printk(KERN_ERR - "kgdboc: Cannot reconfigure while KGDB is connected.\n"); + pr_err("kgdboc: Cannot reconfigure while KGDB is connected.\n"); return -EBUSY; }-- 2.7.4