From 1730f146604ea426e54938cdbcf87df1047ef0dc Mon Sep 17 00:00:00 2001 From: zhong jiang Date: Tue, 2 Aug 2016 14:06:22 -0700 Subject: kexec: add restriction on kexec_load() segment sizes I hit the following issue when run trinity in my system. The kernel is 3.4 version, but mainline has the same issue. The root cause is that the segment size is too large so the kerenl spends too long trying to allocate a page. Other cases will block until the test case quits. Also, OOM conditions will occur. Call Trace: __alloc_pages_nodemask+0x14c/0x8f0 alloc_pages_current+0xaf/0x120 kimage_alloc_pages+0x10/0x60 kimage_alloc_control_pages+0x5d/0x270 machine_kexec_prepare+0xe5/0x6c0 ? kimage_free_page_list+0x52/0x70 sys_kexec_load+0x141/0x600 ? vfs_write+0x100/0x180 system_call_fastpath+0x16/0x1b The patch changes sanity_check_segment_list() to verify that the usage by all segments does not exceed half of memory. [akpm@linux-foundation.org: fix for kexec-return-error-number-directly.patch, update comment] Link: http://lkml.kernel.org/r/1469625474-53904-1-git-send-email-zhongjiang@huawei.com Signed-off-by: zhong jiang Suggested-by: Eric W. Biederman Cc: Vivek Goyal Cc: Dave Young Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kexec_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'kernel') diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 704534029a00..561675589511 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -146,6 +146,7 @@ EXPORT_SYMBOL_GPL(kexec_crash_loaded); * allocating pages whose destination address we do not care about. */ #define KIMAGE_NO_DEST (-1UL) +#define PAGE_COUNT(x) (((x) + PAGE_SIZE - 1) >> PAGE_SHIFT) static struct page *kimage_alloc_page(struct kimage *image, gfp_t gfp_mask, @@ -155,6 +156,7 @@ int sanity_check_segment_list(struct kimage *image) { int i; unsigned long nr_segments = image->nr_segments; + unsigned long total_pages = 0; /* * Verify we have good destination addresses. The caller is @@ -214,6 +216,21 @@ int sanity_check_segment_list(struct kimage *image) return -EINVAL; } + /* + * Verify that no more than half of memory will be consumed. If the + * request from userspace is too large, a large amount of time will be + * wasted allocating pages, which can cause a soft lockup. + */ + for (i = 0; i < nr_segments; i++) { + if (PAGE_COUNT(image->segment[i].memsz) > totalram_pages / 2) + return -EINVAL; + + total_pages += PAGE_COUNT(image->segment[i].memsz); + } + + if (total_pages > totalram_pages / 2) + return -EINVAL; + /* * Verify we have good destination addresses. Normally * the caller is responsible for making certain we don't -- cgit