From: zhong jiang <zhongjiang@xxxxxxxxxx> 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: [<ffffffff81106eac>] __alloc_pages_nodemask+0x14c/0x8f0 [<ffffffff8124c2be>] ? trace_hardirqs_on_thunk+0x3a/0x3c [<ffffffff8124c2be>] ? trace_hardirqs_on_thunk+0x3a/0x3c [<ffffffff8124c2be>] ? trace_hardirqs_on_thunk+0x3a/0x3c [<ffffffff8124c2be>] ? trace_hardirqs_on_thunk+0x3a/0x3c [<ffffffff8124c2be>] ? trace_hardirqs_on_thunk+0x3a/0x3c [<ffffffff8113e5ef>] alloc_pages_current+0xaf/0x120 [<ffffffff810a0da0>] kimage_alloc_pages+0x10/0x60 [<ffffffff810a15ad>] kimage_alloc_control_pages+0x5d/0x270 [<ffffffff81027e85>] machine_kexec_prepare+0xe5/0x6c0 [<ffffffff810a0d52>] ? kimage_free_page_list+0x52/0x70 [<ffffffff810a1921>] sys_kexec_load+0x141/0x600 [<ffffffff8115e6b0>] ? vfs_write+0x100/0x180 [<ffffffff8145fbd9>] 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@xxxxxxxxxxxxxxxxxxxx: fix for kexec-return-error-number-directly.patch, update comment] Link: http://lkml.kernel.org/r/1469625474-53904-1-git-send-email-zhongjiang@xxxxxxxxxx Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx> Suggested-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/kexec_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff -puN kernel/kexec_core.c~kexec-add-restriction-on-kexec_load-segment-sizes kernel/kexec_core.c --- a/kernel/kexec_core.c~kexec-add-restriction-on-kexec_load-segment-sizes +++ a/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 kim { int i; unsigned long nr_segments = image->nr_segments; + unsigned long total_pages = 0; /* * Verify we have good destination addresses. The caller is @@ -215,6 +217,21 @@ int sanity_check_segment_list(struct kim } /* + * 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 * attempt to load the new image into invalid or reserved _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
