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>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
index 673c7dd75ab90c0a6475bacde3adec9743adfd15..ba8d9d7d242bd1a0378ada0ae1a2d27f57ffd749 100644 (file)
--- a/arch/arm/include/asm/bug.h
+++ b/arch/arm/include/asm/bug.h
@@ -88,5 +88,6 @@ extern asmlinkage void c_backtrace(unsigned long fp, int pmode,
 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

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 5199a2bb4111b7bff8c04b1eb4efa2bcdd8bf090..6324f4db9b029ba961b092b47c1bd804bf62647e 100644 (file)
--- a/arch/arm/kernel/process.c
+++ b/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;

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 17d5a785df28b10ee5714246d3ed342192c25e75..64308e3a5d0c4d5cab1a802127dd2507c8892f03 100644 (file)
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -287,6 +287,7 @@ static int __die(const char *str, int err, struct pt_regs *regs)
 
        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));