160 lines
4.6 KiB
Diff
160 lines
4.6 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Chris Coulson <chris.coulson@canonical.com>
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Date: Fri, 29 Apr 2022 21:16:02 +0100
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Subject: [PATCH] commands/boot: Add API to pass context to loader
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Loaders rely on global variables for saving context which is consumed
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in the boot hook and freed in the unload hook. In the case where a loader
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command is executed twice, calling grub_loader_set a second time executes
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the unload hook, but in some cases this runs when the loader's global
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context has already been updated, resulting in the updated context being
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freed and potential use-after-free bugs when the boot hook is subsequently
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called.
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This adds a new API (grub_loader_set_ex) which allows a loader to specify
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context that is passed to its boot and unload hooks. This is an alternative
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to requiring that loaders call grub_loader_unset before mutating their
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global context.
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Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
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(cherry picked from commit 4322a64dde7e8fedb58e50b79408667129d45dd3)
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(cherry picked from commit 937ad0e2159b6b8cb0d2ce3515da3a8b797c7927)
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---
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grub-core/commands/boot.c | 66 +++++++++++++++++++++++++++++++++++++++++------
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include/grub/loader.h | 5 ++++
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2 files changed, 63 insertions(+), 8 deletions(-)
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diff --git a/grub-core/commands/boot.c b/grub-core/commands/boot.c
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index bbca81e947..53691a62d9 100644
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--- a/grub-core/commands/boot.c
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+++ b/grub-core/commands/boot.c
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@@ -27,10 +27,20 @@
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GRUB_MOD_LICENSE ("GPLv3+");
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-static grub_err_t (*grub_loader_boot_func) (void);
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-static grub_err_t (*grub_loader_unload_func) (void);
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+static grub_err_t (*grub_loader_boot_func) (void *);
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+static grub_err_t (*grub_loader_unload_func) (void *);
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+static void *grub_loader_context;
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static int grub_loader_flags;
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+struct grub_simple_loader_hooks
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+{
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+ grub_err_t (*boot) (void);
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+ grub_err_t (*unload) (void);
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+};
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+
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+/* Don't heap allocate this to avoid making grub_loader_set fallible. */
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+static struct grub_simple_loader_hooks simple_loader_hooks;
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+
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struct grub_preboot
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{
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grub_err_t (*preboot_func) (int);
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@@ -44,6 +54,29 @@ static int grub_loader_loaded;
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static struct grub_preboot *preboots_head = 0,
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*preboots_tail = 0;
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+static grub_err_t
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+grub_simple_boot_hook (void *context)
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+{
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+ struct grub_simple_loader_hooks *hooks;
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+
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+ hooks = (struct grub_simple_loader_hooks *) context;
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+ return hooks->boot ();
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+}
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+
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+static grub_err_t
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+grub_simple_unload_hook (void *context)
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+{
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+ struct grub_simple_loader_hooks *hooks;
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+ grub_err_t ret;
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+
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+ hooks = (struct grub_simple_loader_hooks *) context;
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+
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+ ret = hooks->unload ();
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+ grub_memset (hooks, 0, sizeof (*hooks));
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+
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+ return ret;
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+}
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+
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int
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grub_loader_is_loaded (void)
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{
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@@ -110,28 +143,45 @@ grub_loader_unregister_preboot_hook (struct grub_preboot *hnd)
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}
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void
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-grub_loader_set (grub_err_t (*boot) (void),
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- grub_err_t (*unload) (void),
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- int flags)
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+grub_loader_set_ex (grub_err_t (*boot) (void *),
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+ grub_err_t (*unload) (void *),
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+ void *context,
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+ int flags)
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{
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if (grub_loader_loaded && grub_loader_unload_func)
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- grub_loader_unload_func ();
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+ grub_loader_unload_func (grub_loader_context);
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grub_loader_boot_func = boot;
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grub_loader_unload_func = unload;
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+ grub_loader_context = context;
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grub_loader_flags = flags;
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grub_loader_loaded = 1;
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}
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+void
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+grub_loader_set (grub_err_t (*boot) (void),
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+ grub_err_t (*unload) (void),
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+ int flags)
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+{
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+ grub_loader_set_ex (grub_simple_boot_hook,
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+ grub_simple_unload_hook,
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+ &simple_loader_hooks,
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+ flags);
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+
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+ simple_loader_hooks.boot = boot;
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+ simple_loader_hooks.unload = unload;
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+}
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+
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void
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grub_loader_unset(void)
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{
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if (grub_loader_loaded && grub_loader_unload_func)
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- grub_loader_unload_func ();
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+ grub_loader_unload_func (grub_loader_context);
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grub_loader_boot_func = 0;
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grub_loader_unload_func = 0;
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+ grub_loader_context = 0;
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grub_loader_loaded = 0;
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}
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@@ -158,7 +208,7 @@ grub_loader_boot (void)
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return err;
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}
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}
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- err = (grub_loader_boot_func) ();
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+ err = (grub_loader_boot_func) (grub_loader_context);
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for (cur = preboots_tail; cur; cur = cur->prev)
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if (! err)
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diff --git a/include/grub/loader.h b/include/grub/loader.h
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index b208642821..1846fa6c5f 100644
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--- a/include/grub/loader.h
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+++ b/include/grub/loader.h
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@@ -40,6 +40,11 @@ void EXPORT_FUNC (grub_loader_set) (grub_err_t (*boot) (void),
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grub_err_t (*unload) (void),
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int flags);
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+void EXPORT_FUNC (grub_loader_set_ex) (grub_err_t (*boot) (void *),
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+ grub_err_t (*unload) (void *),
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+ void *context,
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+ int flags);
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+
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/* Unset current loader, if any. */
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void EXPORT_FUNC (grub_loader_unset) (void);
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