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grub2/SOURCES/0253-Fix-get_entry_number-w...

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Tue, 4 Dec 2018 10:53:49 +0100
Subject: [PATCH] Fix get_entry_number() wrongly dereferencing the tail pointer
The get_entry_number_helper() function attempts to lookup a boot entry by
either title or id matching the value of an environment variable. If they
are a substring of the variable, the tail pointer is set to the first char
of the remainder of the string.
When get_entry_number() calls this function, it checks if this first char
is a NUL byte, to know if the variable matched correctly. But tail can be
set to NULL as well to indicate that there isn't a remainder in the string.
Resolves: rhbz#1654936
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
grub-core/normal/menu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/grub-core/normal/menu.c b/grub-core/normal/menu.c
index fc25c702f..7e32c498a 100644
--- a/grub-core/normal/menu.c
+++ b/grub-core/normal/menu.c
@@ -563,7 +563,7 @@ get_entry_number (grub_menu_t menu, const char *name)
grub_error_push ();
entry = get_entry_number_helper(menu, val, &tail);
- if (*tail != '\0')
+ if (tail && *tail != '\0')
entry = -1;
grub_error_pop ();