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106 lines
3.5 KiB
106 lines
3.5 KiB
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, 10 Jul 2020 14:41:45 +0100
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Subject: [PATCH] script: Avoid a use-after-free when redefining a function
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during execution
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Defining a new function with the same name as a previously defined
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function causes the grub_script and associated resources for the
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previous function to be freed. If the previous function is currently
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executing when a function with the same name is defined, this results
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in use-after-frees when processing subsequent commands in the original
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function.
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Instead, reject a new function definition if it has the same name as
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a previously defined function, and that function is currently being
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executed. Although a behavioural change, this should be backwards
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compatible with existing configurations because they can't be
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dependent on the current behaviour without being broken.
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Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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Upstream-commit-id: f6253a1f540
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---
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grub-core/script/execute.c | 2 ++
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grub-core/script/function.c | 16 +++++++++++++---
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include/grub/script_sh.h | 2 ++
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grub-core/script/parser.y | 3 ++-
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4 files changed, 19 insertions(+), 4 deletions(-)
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diff --git a/grub-core/script/execute.c b/grub-core/script/execute.c
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index 528ddfd36..a1aadb9ee 100644
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--- a/grub-core/script/execute.c
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+++ b/grub-core/script/execute.c
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@@ -872,7 +872,9 @@ grub_script_function_call (grub_script_function_t func, int argc, char **args)
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old_scope = scope;
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scope = &new_scope;
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+ func->executing++;
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ret = grub_script_execute (func->func);
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+ func->executing--;
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function_return = 0;
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active_loops = loops;
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diff --git a/grub-core/script/function.c b/grub-core/script/function.c
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index d36655e51..3aad04bf9 100644
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--- a/grub-core/script/function.c
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+++ b/grub-core/script/function.c
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@@ -34,6 +34,7 @@ grub_script_function_create (struct grub_script_arg *functionname_arg,
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func = (grub_script_function_t) grub_malloc (sizeof (*func));
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if (! func)
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return 0;
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+ func->executing = 0;
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func->name = grub_strdup (functionname_arg->str);
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if (! func->name)
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@@ -60,10 +61,19 @@ grub_script_function_create (struct grub_script_arg *functionname_arg,
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grub_script_function_t q;
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q = *p;
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- grub_script_free (q->func);
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- q->func = cmd;
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grub_free (func);
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- func = q;
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+ if (q->executing > 0)
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+ {
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+ grub_error (GRUB_ERR_BAD_ARGUMENT,
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+ N_("attempt to redefine a function being executed"));
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+ func = NULL;
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+ }
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+ else
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+ {
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+ grub_script_free (q->func);
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+ q->func = cmd;
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+ func = q;
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+ }
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}
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else
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{
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diff --git a/include/grub/script_sh.h b/include/grub/script_sh.h
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index b382bcf09..6c48e0751 100644
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--- a/include/grub/script_sh.h
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+++ b/include/grub/script_sh.h
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@@ -361,6 +361,8 @@ struct grub_script_function
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/* The next element. */
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struct grub_script_function *next;
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+
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+ unsigned executing;
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};
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typedef struct grub_script_function *grub_script_function_t;
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diff --git a/grub-core/script/parser.y b/grub-core/script/parser.y
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index 4f0ab8319..f80b86b6f 100644
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--- a/grub-core/script/parser.y
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+++ b/grub-core/script/parser.y
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@@ -289,7 +289,8 @@ function: "function" "name"
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grub_script_mem_free (state->func_mem);
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else {
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script->children = state->scripts;
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- grub_script_function_create ($2, script);
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+ if (!grub_script_function_create ($2, script))
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+ grub_script_free (script);
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}
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state->scripts = $<scripts>3;
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