| Message ID | 1429058752-13478-1-git-send-email-roy.franz@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Wed, Apr 15, 2015 at 6:18 AM, Matt Fleming <matt@codeblueprint.co.uk> wrote: > On Tue, 14 Apr, at 05:45:52PM, Roy Franz wrote: >> The boot_params structure has a 32 bit field for storing the address of >> the kernel command line. When the EFI stub allocates memory for the command >> line, it allocates at as low and address as possible, but does not ensure >> that the address of memory allocated is below 4G. >> This patch enforces this limit, and the stub now returns an error if the >> command line buffer is allocated at too high of an address. >> For 32 bit systems, the EFI mandated 1-1 memory mapping ensures >> that all memory is 32 bit addressable, so we don't have a problem. >> Also, mixed-mode booting on EFI platforms does not use the stub >> code, so we don't need to handle the case of booting a 32 bit >> kernel on a 64 bit EFI platform. >> >> Signed-off-by: Roy Franz <roy.franz@linaro.org> >> --- >> arch/x86/boot/compressed/eboot.c | 13 +++++++++++++ >> 1 file changed, 13 insertions(+) >> >> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c >> index ef17683..82dbe27 100644 >> --- a/arch/x86/boot/compressed/eboot.c >> +++ b/arch/x86/boot/compressed/eboot.c >> @@ -1108,6 +1108,19 @@ struct boot_params *make_boot_params(struct efi_config *c) >> cmdline_ptr = efi_convert_cmdline(sys_table, image, &options_size); >> if (!cmdline_ptr) >> goto fail; >> + >> +#ifdef CONFIG_X86_64 >> + /* >> + * hdr->cmd_line_ptr is a 32 bit field, so on 64 bit systems we need >> + * to ensure that the allocated buffer for the commandline is 32 bit >> + * addressable. >> + */ >> + if ((u64)(cmdline_ptr) + options_size > (u64)U32_MAX) { >> + efi_printk(sys_table, "Failed to alloc lowmem for command line\n"); >> + efi_free(sys_table, options_size, (unsigned long)cmdline_ptr); >> + goto fail; >> + } >> +#endif /* CONFIG_X86_64 */ >> hdr->cmd_line_ptr = (unsigned long)cmdline_ptr; >> >> hdr->ramdisk_image = 0; > > Good catch. But actually, we have boot_params->ext_cmd_line_ptr for > exactly this problem. > > So yes, that's a valid bug, but I don't think this is how we should fix > it. Yeah, I guess it shouldn't surprise me that there is support for 64 bit addresses there :) I'l spin another patch that sets boot_params->ext_cmd_line_ptr with the upper 32 bits of the address. Should I conditionalize this with #ifdef CONFIG_X86_64, or just do it unconditionally, with it being a NOP on 32 bit? (I guess I may end up with an extra cast for the 32 bit case) Roy > > -- > Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index ef17683..82dbe27 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -1108,6 +1108,19 @@ struct boot_params *make_boot_params(struct efi_config *c) cmdline_ptr = efi_convert_cmdline(sys_table, image, &options_size); if (!cmdline_ptr) goto fail; + +#ifdef CONFIG_X86_64 + /* + * hdr->cmd_line_ptr is a 32 bit field, so on 64 bit systems we need + * to ensure that the allocated buffer for the commandline is 32 bit + * addressable. + */ + if ((u64)(cmdline_ptr) + options_size > (u64)U32_MAX) { + efi_printk(sys_table, "Failed to alloc lowmem for command line\n"); + efi_free(sys_table, options_size, (unsigned long)cmdline_ptr); + goto fail; + } +#endif /* CONFIG_X86_64 */ hdr->cmd_line_ptr = (unsigned long)cmdline_ptr; hdr->ramdisk_image = 0;
The boot_params structure has a 32 bit field for storing the address of the kernel command line. When the EFI stub allocates memory for the command line, it allocates at as low and address as possible, but does not ensure that the address of memory allocated is below 4G. This patch enforces this limit, and the stub now returns an error if the command line buffer is allocated at too high of an address. For 32 bit systems, the EFI mandated 1-1 memory mapping ensures that all memory is 32 bit addressable, so we don't have a problem. Also, mixed-mode booting on EFI platforms does not use the stub code, so we don't need to handle the case of booting a 32 bit kernel on a 64 bit EFI platform. Signed-off-by: Roy Franz <roy.franz@linaro.org> --- arch/x86/boot/compressed/eboot.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)