+ arm-print-alloc-free-paths-for-address-in-registers.patch added to -mm tree

+ arm-print-alloc-free-paths-for-address-in-registers.patch added to -mm tree

[akpm]

The patch titled
     Subject: arm: print alloc free paths for address in registers
has been added to the -mm tree.  Its filename is
     arm-print-alloc-free-paths-for-address-in-registers.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/arm-print-alloc-free-paths-for-address-in-registers.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/arm-print-alloc-free-paths-for-address-in-registers.patch

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------------------------------------------------------
From: Maninder Singh <maninder1.s@samsung.com>
Subject: arm: print alloc free paths for address in registers

In case of a use after free kernel oops, the freeing path of the object is
required to debug futher.  In most of cases the object address is present
in one of the registers.

Thus check the register's address and if it belongs to slab, print its
alloc and free path.

e.g.  in the below issue register r6 belongs to slab, and a use after free
issue occurred on one of its dereferenced values:

[   20.182197] Unable to handle kernel paging request at virtual address 6b6b6b6f
....
[   20.185035] pc : [<c0538afc>]    lr : [<c0465674>]    psr: 60000013
[   20.185271] sp : c8927d40  ip : ffffefff  fp : c8aa8020
[   20.185462] r10: c8927e10  r9 : 00000001  r8 : 00400cc0
[   20.185674] r7 : 00000000  r6 : c8ab0180  r5 : c1804a80  r4 : c8aa8008
[   20.185924] r3 : c1a5661c  r2 : 00000000  r1 : 6b6b6b6b  r0 : c139bf48
.....
[   20.191499] Register r6 information: slab kmalloc-64 start c8ab0140 data offset 64 pointer offset 0 size 64 allocated at meminfo_proc_show+0x40/0x4fc
[   20.192078]     meminfo_proc_show+0x40/0x4fc
[   20.192263]     seq_read_iter+0x18c/0x4c4
[   20.192430]     proc_reg_read_iter+0x84/0xac
[   20.192617]     generic_file_splice_read+0xe8/0x17c
[   20.192816]     splice_direct_to_actor+0xb8/0x290
[   20.193008]     do_splice_direct+0xa0/0xe0
[   20.193185]     do_sendfile+0x2d0/0x438
[   20.193345]     sys_sendfile64+0x12c/0x140
[   20.193523]     ret_fast_syscall+0x0/0x58
[   20.193695]     0xbeeacde4
[   20.193822]  Free path:
[   20.193935]     meminfo_proc_show+0x5c/0x4fc
[   20.194115]     seq_read_iter+0x18c/0x4c4
[   20.194285]     proc_reg_read_iter+0x84/0xac
[   20.194475]     generic_file_splice_read+0xe8/0x17c
[   20.194685]     splice_direct_to_actor+0xb8/0x290
[   20.194870]     do_splice_direct+0xa0/0xe0
[   20.195014]     do_sendfile+0x2d0/0x438
[   20.195174]     sys_sendfile64+0x12c/0x140
[   20.195336]     ret_fast_syscall+0x0/0x58
[   20.195491]     0xbeeacde4

Link: https://lkml.kernel.org/r/1615891032-29160-3-git-send-email-maninder1.s@samsung.com
Co-developed-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm/include/asm/bug.h |    1 +
 arch/arm/kernel/process.c  |   11 +++++++++++
 arch/arm/kernel/traps.c    |    1 +
 3 files changed, 13 insertions(+)

--- a/arch/arm/include/asm/bug.h~arm-print-alloc-free-paths-for-address-in-registers
+++ a/arch/arm/include/asm/bug.h
@@ -88,5 +88,6 @@ extern asmlinkage void c_backtrace(unsig
 struct mm_struct;
 void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr);
 extern void __show_regs(struct pt_regs *);
+extern void __show_regs_alloc_free(struct pt_regs *regs);
 
 #endif
--- a/arch/arm/kernel/process.c~arm-print-alloc-free-paths-for-address-in-registers
+++ a/arch/arm/kernel/process.c
@@ -92,6 +92,17 @@ void arch_cpu_idle_exit(void)
 	ledtrig_cpu(CPU_LED_IDLE_END);
 }
 
+void __show_regs_alloc_free(struct pt_regs *regs)
+{
+	int i;
+
+	/* check for r0 - r12 only */
+	for (i = 0; i < 13; i++) {
+		pr_alert("Register r%d information:", i);
+		mem_dump_obj((void *)regs->uregs[i]);
+	}
+}
+
 void __show_regs(struct pt_regs *regs)
 {
 	unsigned long flags;
--- a/arch/arm/kernel/traps.c~arm-print-alloc-free-paths-for-address-in-registers
+++ a/arch/arm/kernel/traps.c
@@ -287,6 +287,7 @@ static int __die(const char *str, int er
 
 	print_modules();
 	__show_regs(regs);
+	__show_regs_alloc_free(regs);
 	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
 		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), end_of_stack(tsk));
 
_

Patches currently in -mm which might be from maninder1.s@samsung.com are

mm-slub-fixing-backtrace-of-objects-because-of-redzone-adjustment.patch
mm-slub-add-support-for-free-path-information-of-an-object.patch
arm-print-alloc-free-paths-for-address-in-registers.patch