Re: [PATCH] eventfs: Fix the NULL pointer dereference bug in eventfs_remove_rec()
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2023-09-08 08:26:36
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
On Fri, 8 Sep 2023 15:49:03 +0800 Jinjie Ruan [off-list ref] wrote:
Inject fault while probing btrfs.ko, if kstrdup() fails in
eventfs_prepare_ef() in eventfs_add_dir(), it will return ERR_PTR
to assign file->ef. But the eventfs_remove() check NULL in
trace_module_remove_events(), which causes the below NULL
pointer dereference. So use IS_ERR() to check ef
in eventfs_remove_rec(), and fix the same issue in eventfs_remove().
Could not create tracefs 'raid56_write' directory
Btrfs loaded, zoned=no, fsverity=no
Unable to handle kernel NULL pointer dereference at virtual address 000000000000001c
Mem abort info:
ESR = 0x0000000096000004
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x04: level 0 translation fault
Data abort info:
ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=0000000102544000
[000000000000001c] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in: btrfs(-) libcrc32c xor xor_neon raid6_pq cfg80211 rfkill 8021q garp mrp stp llc ipv6 [last unloaded: btrfs]
CPU: 15 PID: 1343 Comm: rmmod Tainted: G N 6.5.0+ #40
Hardware name: linux,dummy-virt (DT)
pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : eventfs_remove_rec+0x24/0xc0
lr : eventfs_remove+0x68/0x1d8
sp : ffff800082d63b60
x29: ffff800082d63b60 x28: ffffb84b80ddd00c x27: ffffb84b3054ba40
x26: 0000000000000002 x25: ffff800082d63bf8 x24: ffffb84b8398e440
x23: ffffb84b82af3000 x22: dead000000000100 x21: dead000000000122
x20: ffff800082d63bf8 x19: fffffffffffffff4 x18: ffffb84b82508820
x17: 0000000000000000 x16: 0000000000000000 x15: 000083bc876a3166
x14: 000000000000006d x13: 000000000000006d x12: 0000000000000000
x11: 0000000000000001 x10: 00000000000017e0 x9 : 0000000000000001
x8 : 0000000000000000 x7 : 0000000000000000 x6 : ffffb84b84289804
x5 : 0000000000000000 x4 : 9696969696969697 x3 : ffff33a5b7601f38
x2 : 0000000000000000 x1 : ffff800082d63bf8 x0 : fffffffffffffff4
Call trace:
eventfs_remove_rec+0x24/0xc0
eventfs_remove+0x68/0x1d8
remove_event_file_dir+0x88/0x100
event_remove+0x140/0x15c
trace_module_notify+0x1fc/0x230
notifier_call_chain+0x98/0x17c
blocking_notifier_call_chain+0x4c/0x74
__arm64_sys_delete_module+0x1a4/0x298
invoke_syscall+0x44/0x100
el0_svc_common.constprop.1+0x68/0xe0
do_el0_svc+0x1c/0x28
el0_svc+0x3c/0xc4
el0t_64_sync_handler+0xa0/0xc4
el0t_64_sync+0x174/0x178
Code: 5400052c a90153b3 aa0003f3 aa0103f4 (f9401400)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Oops: Fatal exception
SMP: stopping secondary CPUs
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: 0x384b00c00000 from 0xffff800080000000
PHYS_OFFSET: 0xffffcc5b80000000
CPU features: 0x88000203,3c020000,1000421b
Memory Limit: none
Rebooting in 1 seconds..Thanks for reporting the bug!
quoted hunk ↗ jump to hunk
Fixes: 5bdcd5f5331a ("eventfs: Implement removal of meta data from eventfs") Signed-off-by: Jinjie Ruan <redacted> --- fs/tracefs/event_inode.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 237c6f370ad9..e6efa4078f48 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c@@ -693,7 +693,7 @@ static void eventfs_remove_rec(struct eventfs_file *ef, struct list_head *head, { struct eventfs_file *ef_child; - if (!ef) + if (IS_ERR(ef)) return;
But this is not good. Allocater side should handle the error carefully and remove it. e.g.
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 2af92177b765..5a08db957460 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c@@ -2436,6 +2436,7 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file) file->ef = eventfs_add_dir(name, ef_subsystem); if (IS_ERR(file->ef)) { pr_warn("Could not create tracefs '%s' directory\n", name); + file->ef = NULL; return -1; }
Or at least, please use IS_ERR_OR_NULL().
quoted hunk ↗ jump to hunk
/* * Check recursion depth. It should never be greater than 3:@@ -730,7 +730,7 @@ void eventfs_remove(struct eventfs_file *ef) struct dentry *dentry_list = NULL; struct dentry *dentry; - if (!ef) + if (IS_ERR(ef)) return;
Ditto. Thank you,
mutex_lock(&eventfs_mutex); -- 2.34.1
-- Masami Hiramatsu (Google) [off-list ref]