In function perf_event_parse_addr_filter(), the path::dentry of each struct
perf_addr_filter is left unassigned (as it should be) when the pattern
being parsed is related to kernel space. But in function
perf_addr_filter_match() the same dentry'ies are given to d_inode() where
the value is not expected to be NULL, resulting in the following splat:
[ 53.451557] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000058
[ 53.460368] Mem abort info:
[ 53.463134] ESR = 0x96000004
[ 53.466158] Exception class = DABT (current EL), IL = 32 bits
[ 53.472019] SET = 0, FnV = 0
[ 53.475042] EA = 0, S1PTW = 0
[ 53.478150] Data abort info:
[ 53.481000] ISV = 0, ISS = 0x00000004
[ 53.484796] CM = 0, WnR = 0
[ 53.487734] user pgtable: 4k pages, 48-bit VAs, pgdp = 00000000f0644b81
[ 53.494283] [0000000000000058] pgd=0000000000000000
[ 53.499181] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 53.504697] Modules linked in:
[ 53.507726] CPU: 2 PID: 2860 Comm: uname Not tainted 4.18.0-rc5-dirty #288
[ 53.514531] Hardware name: ARM Juno development board (r0) (DT)
[ 53.520392] pstate: 20000085 (nzCv daIf -PAN -UAO)
[ 53.525141] pc : perf_event_mmap+0x2fc/0x5a0
[ 53.529368] lr : perf_event_mmap+0x2c8/0x5a0
[ 53.533593] sp : ffff000010883a10
[ 53.536872] x29: ffff000010883a10 x28: ffff8009749126c0
[ 53.542137] x27: 0000000000000000 x26: ffff800971221000
[ 53.547401] x25: ffff80097678bef0 x24: ffff0000091cb000
[ 53.552665] x23: ffff800971221430 x22: ffff80097100fe00
[ 53.557930] x21: 0000000000001078 x20: ffff0000091af000
[ 53.563194] x19: ffff800971221420 x18: 0000000000006451
[ 53.568457] x17: 000000000000644f x16: ffff000009404790
[ 53.573721] x15: ffff00000932c3b0 x14: 000000000000644e
[ 53.578985] x13: 00000000ed3bb5ef x12: ffff8009711e1de8
[ 53.584248] x11: 0000000000000000 x10: ffff0000091af808
[ 53.589512] x9 : ffff0000091ea000 x8 : ffff0000091af808
[ 53.594776] x7 : 0000000000000002 x6 : ffff8009740c7540
[ 53.600040] x5 : 0000000000000000 x4 : 00000000000067e8
[ 53.605303] x3 : 0000000000000000 x2 : ffff800971131800
[ 53.610567] x1 : 0000000000000002 x0 : 0000000000000000
[ 53.615832] Process uname (pid: 2860, stack limit = 0x000000001cbcca37)
[ 53.622378] Call trace:
[ 53.624798] perf_event_mmap+0x2fc/0x5a0
[ 53.628683] mmap_region+0x124/0x570
[ 53.632221] do_mmap+0x344/0x4f8
[ 53.635414] vm_mmap_pgoff+0xe4/0x110
[ 53.639037] vm_mmap+0x2c/0x40
[ 53.642061] elf_map+0x60/0x108
[ 53.645169] load_elf_binary+0x450/0x12c4
[ 53.649138] search_binary_handler+0x90/0x290
[ 53.653449] __do_execve_file.isra.13+0x6e4/0x858
[ 53.658104] sys_execve+0x3c/0x50
[ 53.661385] el0_svc_naked+0x30/0x34
[ 53.664924] Code: eb02027f 54000300 f9400c45 f94012c6 (f9402ca5)
[ 53.670959] ---[ end trace 3ef799e7226990e4 ]---
This patch is fixing the problem by introducing a new check in function
perf_addr_filter_match() to see if the filter's dentry is NULL.
Fixes: 9511bce9fe8e ("perf/core: Fix bad use of igrab()")
Signed-off-by: Mathieu Poirier <mathieu.poir...@linaro.org>
---
kernel/events/core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8f0434a9951a..a56f10b1e13b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7335,6 +7335,10 @@ static bool perf_addr_filter_match(struct
perf_addr_filter *filter,
struct file *file, unsigned long offset,
unsigned long size)
{
+ /* d_inode(NULL) won't be equal to any mapped user space file */
+ if (!filter->path.dentry)
+ return false;
+
if (d_inode(filter->path.dentry) != file_inode(file))
return false;
--
2.7.4
