From 51e766bcd35e706d8df29dd0fac98871fdced261 Mon Sep 17 00:00:00 2001 From: Wilson Felipe Pereira Date: Tue, 18 Aug 2026 04:53:47 +0000 Subject: [PATCH] init/main: fix false-positive kernel panic on environment variable overwrite In unknown_bootoption(), the limit checking for environment variables sets panic_later *before* checking if the variable already exists in envp_init. If a user passes exactly MAX_INIT_ENVS custom variables and then overwrites the final variable by matching its key, it causes a false-positive hard panic on boot despite not actually exceeding the array bounds or increasing the total variable count. Swapping the order of these checks allows the duplicate check to break out of the loop before the panic flag is erroneously latched. To verify, boot a VM with 31 custom variables (filling the array up to its limit of 32) and then overwrite the very last variable: ENV_VARS=$(for i in {1..31}; do echo -n "var$i=$i "; done) qemu-system-x86_64 -kernel bzImage -append "$ENV_VARS var31=overwrite" Without this patch, the kernel crashes instantly with: Kernel panic - not syncing: Too many boot env vars at 'var31=overwrite' With this patch, the kernel safely overwrites the variable and boots. Link: https://lore.kernel.org/20260818045357.4123784-3-wfelipe@google.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Wilson Felipe Pereira Signed-off-by: Andrew Morton --- init/main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/init/main.c b/init/main.c index 517b76447950..d1cd8efb8238 100644 --- a/init/main.c +++ b/init/main.c @@ -548,12 +548,12 @@ static int __init unknown_bootoption(char *param, char *val, /* Environment option */ unsigned int i; for (i = 0; envp_init[i]; i++) { + if (!strncmp(param, envp_init[i], len+1)) + break; if (i == MAX_INIT_ENVS) { panic_later = "env"; panic_param = param; } - if (!strncmp(param, envp_init[i], len+1)) - break; } envp_init[i] = param; } else {