6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: George Guo [ Upstream commit 485ed44db5694d8d2e5027f63ad608e705286f30 ] When searching the loaded segments for the "kexec" command line marker, the kexec_load(2) path (file_mode == 0) passes the user-space segment buffer straight to strncmp() through a bogus (char __user *) cast. This dereferences a user pointer in kernel context, which is wrong and is flagged by sparse: arch/loongarch/kernel/machine_kexec.c:84:51: sparse: incorrect type in argument 2 (different address spaces) @@ expected char const * @@ got char [noderef] __user * Here copy the marker-sized prefix of each segment into a small on-stack buffer with copy_from_user() before comparing, and skip segments that fault. The subsequent copy_from_user() that stages the full command line into the safe area is left unchanged. Cc: stable@vger.kernel.org Fixes: 4a03b2ac06a5 ("LoongArch: Add kexec support") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202605051639.aEPioXdD-lkp@intel.com/ Co-developed-by: Kexin Liu Signed-off-by: Kexin Liu Signed-off-by: George Guo Signed-off-by: Huacai Chen Signed-off-by: Sasha Levin --- arch/loongarch/kernel/machine_kexec.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c index ce4e132ac1373..7c93e9d1f020b 100644 --- a/arch/loongarch/kernel/machine_kexec.c +++ b/arch/loongarch/kernel/machine_kexec.c @@ -62,6 +62,7 @@ static void kexec_image_info(const struct kimage *kimage) int machine_kexec_prepare(struct kimage *kimage) { int i; + char head[8]; char *bootloader = "kexec"; void *cmdline_ptr = (void *)KEXEC_CMDLINE_ADDR; @@ -72,7 +73,9 @@ int machine_kexec_prepare(struct kimage *kimage) /* Find the command line */ for (i = 0; i < kimage->nr_segments; i++) { - if (!strncmp(bootloader, (char __user *)kimage->segment[i].buf, strlen(bootloader))) { + if (copy_from_user(head, kimage->segment[i].buf, strlen(bootloader))) + continue; + if (!strncmp(bootloader, head, strlen(bootloader))) { if (!copy_from_user(cmdline_ptr, kimage->segment[i].buf, COMMAND_LINE_SIZE)) kimage->arch.cmdline_ptr = (unsigned long)cmdline_ptr; break; -- 2.53.0