[PATCH 1/3] crash: Fix memory reserve dead loop bug in reserve_crashkernel_generic()

[Jinjie Ruan]

If the platform do not support memory above 4G, such as 32 bit arch,
and CRASH_ADDR_LOW_MAX is equal to CRASH_ADDR_HIGH_MAX, the high
crash kernel memory reservation is meaningless and it will cause
dead loop and system stall:

-> reserve_crashkernel_generic() and high is true
 -> memblock_phys_alloc_range() fail and return 0
    -> search_end = CRASH_ADDR_LOW_MAX(same as CRASH_ADDR_HIGH_MAX)
       -> call memblock_phys_alloc_range() again and fail agin.
          -> search_end == CRASH_ADDR_HIGH_MAX satisfy again
	......

However, the current check only considers the case where
CRASH_ADDR_HIGH_MAX is greater than CRASH_ADDR_LOW_MAX. Fix it.

Fixes: 0ab97169aa05 ("crash_core: add generic function to do reservation")
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 kernel/crash_reserve.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
index 5b2722a93a48..e18fb1bb5d28 100644
--- a/kernel/crash_reserve.c
+++ b/kernel/crash_reserve.c
@@ -390,6 +390,11 @@ void __init reserve_crashkernel_generic(char *cmdline,
 	} else if (high) {
 		search_base = CRASH_ADDR_LOW_MAX;
 		search_end = CRASH_ADDR_HIGH_MAX;
+
+		if (search_base >= search_end) {
+			pr_warn("crashkernel high memory reservation failed.\n");
+			return;
+		}
 	}
 
 retry:
@@ -410,7 +415,8 @@ void __init reserve_crashkernel_generic(char *cmdline,
 		 * low memory, fall back to high memory, the minimum required
 		 * low memory will be reserved later.
 		 */
-		if (!high && search_end == CRASH_ADDR_LOW_MAX) {
+		if (!high && search_end == CRASH_ADDR_LOW_MAX &&
+		    CRASH_ADDR_HIGH_MAX > CRASH_ADDR_LOW_MAX) {
 			search_end = CRASH_ADDR_HIGH_MAX;
 			search_base = CRASH_ADDR_LOW_MAX;
 			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
-- 
2.34.1