mm/debug.c: fix __dump_page() for poisoned pages
Evaluating page_mapping() on a poisoned page ends up dereferencing junk and making PF_POISONED_CHECK() considerably crashier than intended: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000006 Mem abort info: ESR = 0x96000005 Exception class = DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000005 CM = 0, WnR = 0 user pgtable: 4k pages, 39-bit VAs, pgdp = 00000000c2f6ac38 [0000000000000006] pgd=0000000000000000, pud=0000000000000000 Internal error: Oops: 96000005 [#1] PREEMPT SMP Modules linked in: CPU: 2 PID: 491 Comm: bash Not tainted 5.0.0-rc1+ #1 Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Dec 17 2018 pstate: 00000005 (nzcv daif -PAN -UAO) pc : page_mapping+0x18/0x118 lr : __dump_page+0x1c/0x398 Process bash (pid: 491, stack limit = 0x000000004ebd4ecd) Call trace: page_mapping+0x18/0x118 __dump_page+0x1c/0x398 dump_page+0xc/0x18 remove_store+0xbc/0x120 dev_attr_store+0x18/0x28 sysfs_kf_write+0x40/0x50 kernfs_fop_write+0x130/0x1d8 __vfs_write+0x30/0x180 vfs_write+0xb4/0x1a0 ksys_write+0x60/0xd0 __arm64_sys_write+0x18/0x20 el0_svc_common+0x94/0xf8 el0_svc_handler+0x68/0x70 el0_svc+0x8/0xc Code: f9400401 d1000422 f240003f 9a801040 (f9400402) ---[ end trace cdb5eb5bf435cecb ]--- Fix that by not inspecting the mapping until we've determined that it's likely to be valid. Now the above condition still ends up stopping the kernel, but in the correct manner: page:ffffffbf20000000 is uninitialized and poisoned raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) ------------[ cut here ]------------ kernel BUG at ./include/linux/mm.h:1006! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 483 Comm: bash Not tainted 5.0.0-rc1+ #3 Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Dec 17 2018 pstate: 40000005 (nZcv daif -PAN -UAO) pc : remove_store+0xbc/0x120 lr : remove_store+0xbc/0x120 ... Link: http://lkml.kernel.org/r/03b53ee9d7e76cda4b9b5e1e31eea080db033396.1550071778.git.robin.murphy@arm.com Fixes: 1c6fb1d8 ("mm: print more information about mapping in __dump_page") Signed-off-by:Robin Murphy <robin.murphy@arm.com> Acked-by:
Michal Hocko <mhocko@suse.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
parent
b2b46993
Please register or sign in to comment