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shim: Prevent shim to set itself as a second stage loader

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When shim is invoked from a relative path (e.g: from the UEFI shell), the
Loaded Image handle LoadOptions can be set to the binary relative path.

But the is_our_path() function only checks if LoadOptions is set to the
absolute path of shim to ignore it. So if a relative path is there, shim
would set itself as the secondary loader and invoke itself in a loop.

To prevent that, use the path in LoadOptions to calculate the absolute
path and compare it with the one in the Loader Image handle FilePath.

Resolves: bz#1622485

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maran Wilson maran.wilson@oracle.com
Tested-by: Maran Wilson maran.wilson@oracle.com
Upstream-commit-id: e563bc3dcd1
This commit is contained in:
Javier Martinez Canillas 2018-09-07 15:10:51 +02:00 committed by Peter Jones
parent 79be2af526
commit 818a0dbd24
1 changed files with 14 additions and 3 deletions
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17
shim.c
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@ -2086,21 +2086,32 @@ get_load_option_optional_data(UINT8 *data, UINTN data_size,
return EFI_SUCCESS;
}
static int is_our_path(EFI_LOADED_IMAGE *li, CHAR16 *path, UINTN len)
static int is_our_path(EFI_LOADED_IMAGE *li, CHAR16 *path)
{
CHAR16 *dppath = NULL;
CHAR16 *PathName = NULL;
EFI_STATUS efi_status;
int ret = 1;
dppath = DevicePathToStr(li->FilePath);
if (!dppath)
return 0;
efi_status = generate_path_from_image_path(li, path, &PathName);
if (EFI_ERROR(efi_status)) {
perror(L"Unable to generate path %s: %r\n", path,
efi_status);
goto done;
}
dprint(L"dppath: %s\n", dppath);
dprint(L"path: %s\n", path);
if (StrnCaseCmp(dppath, path, len))
if (StrnCaseCmp(dppath, PathName, strlen(dppath)))
ret = 0;
done:
FreePool(dppath);
FreePool(PathName);
return ret;
}
@ -2289,7 +2300,7 @@ EFI_STATUS set_second_stage (EFI_HANDLE image_handle)
* which is just cruel... So yeah, just don't use it.
*/
if (strings == 1 && is_our_path(li, start, loader_len))
if (strings == 1 && is_our_path(li, start))
return EFI_SUCCESS;
/*