* [PATCH] module: fix signature check failures when using in-kernel decompression
@ 2022-01-14 0:51 Dmitry Torokhov
2022-01-14 16:12 ` Doug Anderson
2022-01-14 17:43 ` Luis Chamberlain
0 siblings, 2 replies; 3+ messages in thread
From: Dmitry Torokhov @ 2022-01-14 0:51 UTC (permalink / raw)
To: Luis Chamberlain; +Cc: Jessica Yu, linux-kernel
The new flag MODULE_INIT_COMPRESSED_FILE unintentionally trips check in
module_sig_check(). The check was supposed to catch case when version
info or magic was removed from a signed module, making signature
invalid, but it was coded too broadly and was catching this new flag as
well.
Change the check to only test the 2 particular flags affecting signature
validity.
Fixes: b1ae6dc41eaa ("module: add in-kernel support for decompressing")
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
kernel/module.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 201398d58079..24dab046e16c 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2883,12 +2883,13 @@ static int module_sig_check(struct load_info *info, int flags)
const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
const char *reason;
const void *mod = info->hdr;
-
+ bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
+ MODULE_INIT_IGNORE_VERMAGIC);
/*
- * Require flags == 0, as a module with version information
- * removed is no longer the module that was signed
+ * Do not allow mangled modules as a module with version information
+ * removed is no longer the module that was signed.
*/
- if (flags == 0 &&
+ if (!mangled_module &&
info->len > markerlen &&
memcmp(mod + info->len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
/* We truncate the module to discard the signature */
--
2.34.1.703.g22d0c6ccf7-goog
--
Dmitry
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] module: fix signature check failures when using in-kernel decompression
2022-01-14 0:51 [PATCH] module: fix signature check failures when using in-kernel decompression Dmitry Torokhov
@ 2022-01-14 16:12 ` Doug Anderson
2022-01-14 17:43 ` Luis Chamberlain
1 sibling, 0 replies; 3+ messages in thread
From: Doug Anderson @ 2022-01-14 16:12 UTC (permalink / raw)
To: Dmitry Torokhov; +Cc: Luis Chamberlain, Jessica Yu, LKML
Hi,
On Thu, Jan 13, 2022 at 4:52 PM Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
>
> The new flag MODULE_INIT_COMPRESSED_FILE unintentionally trips check in
> module_sig_check(). The check was supposed to catch case when version
> info or magic was removed from a signed module, making signature
> invalid, but it was coded too broadly and was catching this new flag as
> well.
>
> Change the check to only test the 2 particular flags affecting signature
> validity.
>
> Fixes: b1ae6dc41eaa ("module: add in-kernel support for decompressing")
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> ---
> kernel/module.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 201398d58079..24dab046e16c 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2883,12 +2883,13 @@ static int module_sig_check(struct load_info *info, int flags)
> const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
> const char *reason;
> const void *mod = info->hdr;
> -
> + bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
> + MODULE_INIT_IGNORE_VERMAGIC);
> /*
> - * Require flags == 0, as a module with version information
> - * removed is no longer the module that was signed
> + * Do not allow mangled modules as a module with version information
> + * removed is no longer the module that was signed.
> */
> - if (flags == 0 &&
> + if (!mangled_module &&
Seems reasonable to me. I guess the only question in my mind is
whether this is the best way to handle "unknown" new flags. If someone
introduces a new flag to "uapi/linux/module.h" should we consider it
as "mangled" or not? Given that I can't predict the future and the
comments seem to indicate that we're only trying to detect
version-related issues, your choice seems OK to me.
Reviewed-by: Douglas Anderson <dianders@chromium.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] module: fix signature check failures when using in-kernel decompression
2022-01-14 0:51 [PATCH] module: fix signature check failures when using in-kernel decompression Dmitry Torokhov
2022-01-14 16:12 ` Doug Anderson
@ 2022-01-14 17:43 ` Luis Chamberlain
1 sibling, 0 replies; 3+ messages in thread
From: Luis Chamberlain @ 2022-01-14 17:43 UTC (permalink / raw)
To: Dmitry Torokhov; +Cc: Jessica Yu, linux-kernel
On Thu, Jan 13, 2022 at 04:51:52PM -0800, Dmitry Torokhov wrote:
> The new flag MODULE_INIT_COMPRESSED_FILE unintentionally trips check in
> module_sig_check(). The check was supposed to catch case when version
> info or magic was removed from a signed module, making signature
> invalid, but it was coded too broadly and was catching this new flag as
> well.
>
> Change the check to only test the 2 particular flags affecting signature
> validity.
>
> Fixes: b1ae6dc41eaa ("module: add in-kernel support for decompressing")
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Queued on to modules-next.
Luis
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-01-14 0:51 [PATCH] module: fix signature check failures when using in-kernel decompression Dmitry Torokhov
2022-01-14 16:12 ` Doug Anderson
2022-01-14 17:43 ` Luis Chamberlain
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