From fe76407da71233f8b172e2eabaf58a9d3dccf894 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Thu, 7 Nov 2013 16:29:15 +0000 Subject: [PATCH] slub: Handle NULL parameter in kmem_cache_flags commit c6f58d9b362b45c52afebe4342c9137d0dabe47f upstream. Andreas Herrmann writes: When I've used slub_debug kernel option (e.g. "slub_debug=,skbuff_fclone_cache" or similar) on a debug session I've seen a panic like: Highbank #setenv bootargs console=ttyAMA0 root=/dev/sda2 kgdboc.kgdboc=ttyAMA0,115200 slub_debug=,kmalloc-4096 earlyprintk=ttyAMA0 ... Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = c0004000 [00000000] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: CPU: 0 PID: 0 Comm: swapper Tainted: G W 3.12.0-00048-gbe408cd #314 task: c0898360 ti: c088a000 task.ti: c088a000 PC is at strncmp+0x1c/0x84 LR is at kmem_cache_flags.isra.46.part.47+0x44/0x60 pc : [] lr : [] psr: 200001d3 sp : c088bea8 ip : c088beb8 fp : c088beb4 r10: 00000000 r9 : 413fc090 r8 : 00000001 r7 : 00000000 r6 : c2984a08 r5 : c0966e78 r4 : 00000000 r3 : 0000006b r2 : 0000000c r1 : 00000000 r0 : c2984a08 Flags: nzCv IRQs off FIQs off Mode SVC_32 ISA ARM Segment kernel Control: 10c5387d Table: 0000404a DAC: 00000015 Process swapper (pid: 0, stack limit = 0xc088a248) Stack: (0xc088bea8 to 0xc088c000) bea0: c088bed4 c088beb8 c0110a3c c02c6d90 c0966e78 00000040 bec0: ef001f00 00000040 c088bf14 c088bed8 c0112070 c0110a04 00000005 c010fac8 bee0: c088bf5c c088bef0 c010fac8 ef001f00 00000040 00000000 00000040 00000001 bf00: 413fc090 00000000 c088bf34 c088bf18 c0839190 c0112040 00000000 ef001f00 bf20: 00000000 00000000 c088bf54 c088bf38 c0839200 c083914c 00000006 c0961c4c bf40: c0961c28 00000000 c088bf7c c088bf58 c08392ac c08391c0 c08a2ed8 c0966e78 bf60: c086b874 c08a3f50 c0961c28 00000001 c088bfb4 c088bf80 c083b258 c0839248 bf80: 2f800000 0f000000 c08935b4 ffffffff c08cd400 ffffffff c08cd400 c0868408 bfa0: c29849c0 00000000 c088bff4 c088bfb8 c0824974 c083b1e4 ffffffff ffffffff bfc0: c08245c0 00000000 00000000 c0868408 00000000 10c5387d c0892bcc c0868404 bfe0: c0899440 0000406a 00000000 c088bff8 00008074 c0824824 00000000 00000000 [] (strncmp+0x1c/0x84) from [] (kmem_cache_flags.isra.46.part.47+0x44/0x60) [] (kmem_cache_flags.isra.46.part.47+0x44/0x60) from [] (__kmem_cache_create+0x3c/0x410) [] (__kmem_cache_create+0x3c/0x410) from [] (create_boot_cache+0x50/0x74) [] (create_boot_cache+0x50/0x74) from [] (create_kmalloc_cache+0x4c/0x88) [] (create_kmalloc_cache+0x4c/0x88) from [] (create_kmalloc_caches+0x70/0x114) [] (create_kmalloc_caches+0x70/0x114) from [] (kmem_cache_init+0x80/0xe0) [] (kmem_cache_init+0x80/0xe0) from [] (start_kernel+0x15c/0x318) [] (start_kernel+0x15c/0x318) from [<00008074>] (0x8074) Code: e3520000 01a00002 089da800 e5d03000 (e5d1c000) ---[ end trace 1b75b31a2719ed1d ]--- Kernel panic - not syncing: Fatal exception Problem is that slub_debug option is not parsed before create_boot_cache is called. Solve this by changing slub_debug to early_param. Kernels 3.11, 3.10 are also affected. I am not sure about older kernels. Christoph Lameter explains: kmem_cache_flags may be called with NULL parameter during early boot. Skip the test in that case. Reported-by: Andreas Herrmann Signed-off-by: Christoph Lameter Signed-off-by: Pekka Enberg Signed-off-by: Greg Kroah-Hartman --- mm/slub.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 57707f0..c34bd44 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1201,8 +1201,8 @@ static unsigned long kmem_cache_flags(unsigned long object_size, /* * Enable debugging if selected on the kernel commandline. */ - if (slub_debug && (!slub_debug_slabs || - !strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)))) + if (slub_debug && (!slub_debug_slabs || (name && + !strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs))))) flags |= slub_debug; return flags; -- 2.7.4