| Message ID | 1618284216-17004-1-git-send-email-yangtiezhu@loongson.cn (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [RFC,v2] module: Use ARG_MAX as second argument of strndup_user() in load_module() | expand |
diff --git a/kernel/module.c b/kernel/module.c index 3047935..30d320b 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3998,7 +3998,7 @@ static int load_module(struct load_info *info, const char __user *uargs, flush_module_icache(mod); /* Now copy in args */ - mod->args = strndup_user(uargs, ~0UL >> 1); + mod->args = strndup_user(uargs, ARG_MAX); if (IS_ERR(mod->args)) { err = PTR_ERR(mod->args); goto free_arch_cleanup;
When update kernel with the latest mips-next, we can not login through a graphical interface, this is because drm radeon GPU driver does not work, we can not see the boot message "[drm] radeon kernel modesetting enabled." through the serial console. drivers/gpu/drm/radeon/radeon_drv.c static int __init radeon_module_init(void) { [...] DRM_INFO("radeon kernel modesetting enabled.\n"); [...] } I use git bisect to find out the commit 04324f44cb69 ("MIPS: Remove get_fs/set_fs") is the first bad commit. I analysis and test the changes in the above first bad commit and then find out the following obvious difference which leads to the login issue. arch/mips/include/asm/uaccess.h static inline long strnlen_user(const char __user *s, long n) { [...] if (!access_ok(s, n)) return -0; [...] } I use dump_stack() to find out the following call trace: load_module() strndup_user() strnlen_user() load_module() failed in the following error path, we can see that the second argument of strndup_user() is very big. static int load_module(struct load_info *info, const char __user *uargs, int flags) { [...] mod->args = strndup_user(uargs, ~0UL >> 1); if (IS_ERR(mod->args)) { err = PTR_ERR(mod->args); goto free_arch_cleanup; } [...] } As discussed earlier [1], it seems that just modify the exception check condition in strnlen_user() to fix load_module() failure, like this: arch/mips/include/asm/uaccess.h static inline long strnlen_user(const char __user *s, long n) { [...] if (!access_ok(s, 1)) return 0; [...] } At the other hand, I search strndup_user() in the kernel tree, the second argument of them are almost a macro or a fixed value which is relatively small, such as PAGE_SIZE, PATH_MAX. So I think maybe we can use ARG_MAX as second argument of strndup_user() in load_module(). With this patch, the load_module() failure disappered and we can login normally through a graphical interface. [1] https://lore.kernel.org/patchwork/patch/1411214/ Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> --- v2: Update the commit message to avoid using diff content - patch(1) might not work kernel/module.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)