The udl driver crashes when fbdefio is used. The crash can be reproduced
with this sequence:
1. echo 1 >/sys/module/udl/parameters/fb_defio
2. run some program that maps the framebuffer, such as 'links -g' or 'fbi'
3. allocate memory to the point where the machine starts swapping
The reason for the crash is that udl_gem_get_pages calls drm_gem_get_pages
and drm_gem_get_pages allocates the pages using shmem_read_mapping_page.
The shmem pages are kept on the memory management lists using the
page->lru entry.
However, fbdefio reuses the page->lru entry for the list of pages that
were modified, so the memory management lists are corrupted and the
machine crashes when vmscan starts to scan memory.
I fixed this crash by allocating pages with "alloc_page" instead. The
pages allocated with "alloc_page" have page->lru unused, and thus the
system doesn't crash when fbdefio uses it.
Unable to handle kernel paging request at virtual address dead000000000200
Mem abort info:
ESR = 0x96000044
Exception class = DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
Data abort info:
ISV = 0, ISS = 0x00000044
CM = 0, WnR = 1
[dead000000000200] address between user and kernel address ranges
Internal error: Oops: 96000044 [#1] PREEMPT SMP
Modules linked in: ip6table_filter ip6_tables iptable_filter ip_tables x_tables
af_packet autofs4 udl drm_kms_helper cfbfillrect syscopyarea cfbimgblt
sysfillrect sysimgblt fb_sys_fops cfbcopyarea fb font drm
drm_panel_orientation_quirks mousedev hid_generic usbhid hid binfmt_misc
snd_usb_audio snd_hwdep snd_usbmidi_lib snd_rawmidi snd_pcm snd_timer snd
soundcore ipv6 aes_ce_blk crypto_simd cryptd aes_ce_cipher crc32_ce ghash_ce
gf128mul aes_arm64 sha2_ce sha256_arm64 sha1_ce sha1_generic xhci_plat_hcd
xhci_hcd sd_mod usbcore usb_common mvpp2 unix
CPU: 0 PID: 39 Comm: kswapd0 Not tainted 4.16.12 #3
Hardware name: Marvell 8040 MACHIATOBin (DT)
pstate: 00000085 (nzcv daIf -PAN -UAO)
pc : isolate_lru_pages.isra.16+0x23c/0x2b0
lr : isolate_lru_pages.isra.16+0x104/0x2b0
sp : ffffffc13a897ac0
x29: ffffffc13a897ac0 x28: 0000000000000003
x27: 0000000000000003 x26: 0000000000000004
x25: ffffff80087e84a0 x24: ffffffc13a897b68
x23: ffffffbf04cefc60 x22: ffffffc13a897e44
x21: 0000000000000009 x20: ffffffc13a897c00
x19: ffffffc13a897b40 x18: ffffffbf04d39000
x17: 00000000fffffff8 x16: ffffffbf00000000
x15: 0000000000000006 x14: 0000000000000000
x13: 00000000000001aa x12: 400000000004001c
x11: 0000000000000001 x10: 0000000000000001
x9 : 00000000000ee3ac x8 : 00000000000004a0
x7 : ffffff80087e84a0 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000002
x3 : ffffff80087e84a0 x2 : 0000000000000200
x1 : dead000000000200 x0 : 400000000004001c
Process kswapd0 (pid: 39, stack limit = 0x0000000097f25571)
Call trace:
isolate_lru_pages.isra.16+0x23c/0x2b0
shrink_inactive_list+0xe4/0x3b0
shrink_node_memcg.constprop.19+0x374/0x630
shrink_node+0x64/0x1c8
kswapd+0x340/0x568
kthread+0x118/0x120
ret_from_fork+0x10/0x18
Code: d2804002 f85e02e0 f85e02ec f9000461 (f9000023)
---[ end trace f9f3ad3856cb2ef3 ]---
note: kswapd0[39] exited with preempt_count 1
Signed-off-by: Mikulas Patocka <mpato...@redhat.com>
Cc: sta...@vger.kernel.org
---
drivers/gpu/drm/udl/udl_gem.c | 31 +++++++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)
Index: linux-4.16.12/drivers/gpu/drm/udl/udl_gem.c
===================================================================
--- linux-4.16.12.orig/drivers/gpu/drm/udl/udl_gem.c 2018-01-10
09:31:23.000000000 +0100
+++ linux-4.16.12/drivers/gpu/drm/udl/udl_gem.c 2018-05-29 17:46:10.000000000
+0200
@@ -130,28 +130,51 @@ int udl_gem_fault(struct vm_fault *vmf)
int udl_gem_get_pages(struct udl_gem_object *obj)
{
struct page **pages;
+ int npages, i;
if (obj->pages)
return 0;
- pages = drm_gem_get_pages(&obj->base);
- if (IS_ERR(pages))
- return PTR_ERR(pages);
+ npages = obj->base.size >> PAGE_SHIFT;
+
+ pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
+ if (!pages)
+ return -ENOMEM;
+
+ for (i = 0; i < npages; i++) {
+ struct page *p = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!p)
+ goto fail;
+ pages[i] = p;
+ }
obj->pages = pages;
return 0;
+
+fail:
+ while (i--)
+ put_page(pages[i]);
+ kvfree(pages);
+ return -ENOMEM;
}
void udl_gem_put_pages(struct udl_gem_object *obj)
{
+ int npages, i;
+
if (obj->base.import_attach) {
kvfree(obj->pages);
obj->pages = NULL;
return;
}
- drm_gem_put_pages(&obj->base, obj->pages, false, false);
+ npages = obj->base.size >> PAGE_SHIFT;
+
+ for (i = 0; i < npages; i++)
+ put_page(obj->pages[i]);
+
+ kvfree(obj->pages);
obj->pages = NULL;
}
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