* KASAN: use-after-free Read in smk_write_relabel_self
@ 2020-06-08 21:56 syzbot
2020-07-08 20:15 ` [PATCH] Smack: fix use-after-free in smk_write_relabel_self() Eric Biggers
0 siblings, 1 reply; 5+ messages in thread
From: syzbot @ 2020-06-08 21:56 UTC (permalink / raw)
To: casey, jmorris, linux-kernel, linux-security-module, serge,
syzkaller-bugs
Hello,
syzbot found the following crash on:
HEAD commit: acf25aa6 Merge tag 'Smack-for-5.8' of git://github.com/csc..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11cd3ea6100000
kernel config: https://syzkaller.appspot.com/x/.config?x=3d66e6915128ae67
dashboard link: https://syzkaller.appspot.com/bug?extid=e6416dabb497a650da40
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10654fd2100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107beea6100000
Bisection is inconclusive: the bug happens on the oldest tested release.
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=129e16fe100000
final crash: https://syzkaller.appspot.com/x/report.txt?x=119e16fe100000
console output: https://syzkaller.appspot.com/x/log.txt?x=169e16fe100000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in smk_destroy_label_list security/smack/smackfs.c:1975 [inline]
BUG: KASAN: use-after-free in smk_write_relabel_self+0x2f6/0x480 security/smack/smackfs.c:2748
Read of size 8 at addr ffff88809184bec0 by task syz-executor032/6852
CPU: 0 PID: 6852 Comm: syz-executor032 Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1e9/0x30e lib/dump_stack.c:118
print_address_description+0x66/0x5a0 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report+0x132/0x1d0 mm/kasan/report.c:530
smk_destroy_label_list security/smack/smackfs.c:1975 [inline]
smk_write_relabel_self+0x2f6/0x480 security/smack/smackfs.c:2748
__vfs_write+0x9c/0x6e0 fs/read_write.c:495
__kernel_write+0x120/0x350 fs/read_write.c:516
write_pipe_buf+0xf9/0x150 fs/splice.c:799
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
default_file_splice_write fs/splice.c:811 [inline]
do_splice_from fs/splice.c:847 [inline]
direct_splice_actor+0x1eb/0x2a0 fs/splice.c:1016
splice_direct_to_actor+0x4a2/0xb60 fs/splice.c:971
do_splice_direct+0x201/0x340 fs/splice.c:1059
do_sendfile+0x809/0xfe0 fs/read_write.c:1521
__do_sys_sendfile64 fs/read_write.c:1582 [inline]
__se_sys_sendfile64 fs/read_write.c:1568 [inline]
__x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1568
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x446a29
Code: e8 bc b4 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 ab 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f662054fdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00000000006dbc88 RCX: 0000000000446a29
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000006
RBP: 00000000006dbc80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000100000064 R11: 0000000000000246 R12: 00000000006dbc8c
R13: 00007fffa294e1ef R14: 00007f66205509c0 R15: 0000000000000001
Allocated by task 6850:
save_stack mm/kasan/common.c:48 [inline]
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
smk_parse_label_list+0xff/0x280 security/smack/smackfs.c:1955
smk_write_relabel_self+0x190/0x480 security/smack/smackfs.c:2744
__vfs_write+0x9c/0x6e0 fs/read_write.c:495
__kernel_write+0x120/0x350 fs/read_write.c:516
write_pipe_buf+0xf9/0x150 fs/splice.c:799
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
default_file_splice_write fs/splice.c:811 [inline]
do_splice_from fs/splice.c:847 [inline]
direct_splice_actor+0x1eb/0x2a0 fs/splice.c:1016
splice_direct_to_actor+0x4a2/0xb60 fs/splice.c:971
do_splice_direct+0x201/0x340 fs/splice.c:1059
do_sendfile+0x809/0xfe0 fs/read_write.c:1521
__do_sys_sendfile64 fs/read_write.c:1582 [inline]
__se_sys_sendfile64 fs/read_write.c:1568 [inline]
__x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1568
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
Freed by task 6850:
save_stack mm/kasan/common.c:48 [inline]
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x220 mm/slab.c:3757
smk_destroy_label_list security/smack/smackfs.c:1976 [inline]
smk_write_relabel_self+0x302/0x480 security/smack/smackfs.c:2748
__vfs_write+0x9c/0x6e0 fs/read_write.c:495
__kernel_write+0x120/0x350 fs/read_write.c:516
write_pipe_buf+0xf9/0x150 fs/splice.c:799
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
default_file_splice_write fs/splice.c:811 [inline]
do_splice_from fs/splice.c:847 [inline]
direct_splice_actor+0x1eb/0x2a0 fs/splice.c:1016
splice_direct_to_actor+0x4a2/0xb60 fs/splice.c:971
do_splice_direct+0x201/0x340 fs/splice.c:1059
do_sendfile+0x809/0xfe0 fs/read_write.c:1521
__do_sys_sendfile64 fs/read_write.c:1582 [inline]
__se_sys_sendfile64 fs/read_write.c:1568 [inline]
__x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1568
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
The buggy address belongs to the object at ffff88809184bec0
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
32-byte region [ffff88809184bec0, ffff88809184bee0)
The buggy address belongs to the page:
page:ffffea00024612c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809184bfc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029a8788 ffffea0002a351c8 ffff8880aa4001c0
raw: ffff88809184bfc1 ffff88809184b000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88809184bd80: 00 00 00 fc fc fc fc fc fb fb fb fb fc fc fc fc
ffff88809184be00: 00 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
>ffff88809184be80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
^
ffff88809184bf00: fb fb fb fb fc fc fc fc 00 00 00 fc fc fc fc fc
ffff88809184bf80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] Smack: fix use-after-free in smk_write_relabel_self() 2020-06-08 21:56 KASAN: use-after-free Read in smk_write_relabel_self syzbot @ 2020-07-08 20:15 ` Eric Biggers 2020-07-16 0:27 ` Sasha Levin 2020-07-21 0:38 ` Eric Biggers 0 siblings, 2 replies; 5+ messages in thread From: Eric Biggers @ 2020-07-08 20:15 UTC (permalink / raw) To: linux-security-module, Casey Schaufler, James Morris, Serge E . Hallyn Cc: syzkaller-bugs, linux-kernel, stable, syzbot+e6416dabb497a650da40 From: Eric Biggers <ebiggers@google.com> smk_write_relabel_self() frees memory from the task's credentials with no locking, which can easily cause a use-after-free because multiple tasks can share the same credentials structure. Fix this by using prepare_creds() and commit_creds() to correctly modify the task's credentials. Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self": #include <fcntl.h> #include <pthread.h> #include <unistd.h> static void *thrproc(void *arg) { int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY); for (;;) write(fd, "foo", 3); } int main() { pthread_t t; pthread_create(&t, NULL, thrproc, NULL); thrproc(NULL); } Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com Fixes: 38416e53936e ("Smack: limited capability for changing process label") Cc: <stable@vger.kernel.org> # v4.4+ Signed-off-by: Eric Biggers <ebiggers@google.com> --- security/smack/smackfs.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c index c21b656b3263..840a192e9337 100644 --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -2720,7 +2720,6 @@ static int smk_open_relabel_self(struct inode *inode, struct file *file) static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { - struct task_smack *tsp = smack_cred(current_cred()); char *data; int rc; LIST_HEAD(list_tmp); @@ -2745,11 +2744,21 @@ static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf, kfree(data); if (!rc || (rc == -EINVAL && list_empty(&list_tmp))) { + struct cred *new; + struct task_smack *tsp; + + new = prepare_creds(); + if (!new) { + rc = -ENOMEM; + goto out; + } + tsp = smack_cred(new); smk_destroy_label_list(&tsp->smk_relabel); list_splice(&list_tmp, &tsp->smk_relabel); + commit_creds(new); return count; } - +out: smk_destroy_label_list(&list_tmp); return rc; } -- 2.27.0 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] Smack: fix use-after-free in smk_write_relabel_self() 2020-07-08 20:15 ` [PATCH] Smack: fix use-after-free in smk_write_relabel_self() Eric Biggers @ 2020-07-16 0:27 ` Sasha Levin 2020-07-21 0:38 ` Eric Biggers 1 sibling, 0 replies; 5+ messages in thread From: Sasha Levin @ 2020-07-16 0:27 UTC (permalink / raw) To: Sasha Levin, Eric Biggers, Eric Biggers, linux-security-module Cc: syzkaller-bugs, linux-kernel, stable Hi [This is an automated email] This commit has been processed because it contains a "Fixes:" tag fixing commit: 38416e53936e ("Smack: limited capability for changing process label"). The bot has tested the following trees: v5.7.8, v5.4.51, v4.19.132, v4.14.188, v4.9.230, v4.4.230. v5.7.8: Build OK! v5.4.51: Build OK! v4.19.132: Failed to apply! Possible dependencies: b17103a8b8ae9 ("Smack: Abstract use of cred security blob") v4.14.188: Failed to apply! Possible dependencies: 03450e271a160 ("fs: add ksys_fchmod() and do_fchmodat() helpers and ksys_chmod() wrapper; remove in-kernel calls to syscall") 312db1aa1dc7b ("fs: add ksys_mount() helper; remove in-kernel calls to sys_mount()") 3a18ef5c1b393 ("fs: add ksys_umount() helper; remove in-kernel call to sys_umount()") 447016e968196 ("fs: add ksys_chdir() helper; remove in-kernel calls to sys_chdir()") 819671ff849b0 ("syscalls: define and explain goal to not call syscalls in the kernel") 9481769208b5e ("->file_open(): lose cred argument") a16fe33ab5572 ("fs: add ksys_chroot() helper; remove-in kernel calls to sys_chroot()") ae2bb293a3e8a ("get rid of cred argument of vfs_open() and do_dentry_open()") af04fadcaa932 ("Revert "fs: fold open_check_o_direct into do_dentry_open"") b17103a8b8ae9 ("Smack: Abstract use of cred security blob") c7248321a3d42 ("fs: add ksys_dup{,3}() helper; remove in-kernel calls to sys_dup{,3}()") d19dfe58b7ecb ("Smack: Privilege check on key operations") dcb569cf6ac99 ("Smack: ptrace capability use fixes") e3f20ae21079e ("security_file_open(): lose cred argument") e7a3e8b2edf54 ("fs: add ksys_write() helper; remove in-kernel calls to sys_write()") v4.9.230: Failed to apply! Possible dependencies: 078c73c63fb28 ("apparmor: add profile and ns params to aa_may_manage_policy()") 121d4a91e3c12 ("apparmor: rename sid to secid") 12557dcba21b0 ("apparmor: move lib definitions into separate lib include") 2bd8dbbf22fe9 ("apparmor: add ns being viewed as a param to policy_view_capable()") 5ac8c355ae001 ("apparmor: allow introspecting the loaded policy pre internal transform") 637f688dc3dc3 ("apparmor: switch from profiles to using labels on contexts") 73688d1ed0b8f ("apparmor: refactor prepare_ns() and make usable from different views") 9481769208b5e ("->file_open(): lose cred argument") 98849dff90e27 ("apparmor: rename namespace to ns to improve code line lengths") 9a2d40c12d00e ("apparmor: add strn version of aa_find_ns") a6f233003b1af ("apparmor: allow specifying the profile doing the management") b17103a8b8ae9 ("Smack: Abstract use of cred security blob") cff281f6861e7 ("apparmor: split apparmor policy namespaces code into its own file") d19dfe58b7ecb ("Smack: Privilege check on key operations") dcb569cf6ac99 ("Smack: ptrace capability use fixes") f28e783ff668c ("Smack: Use cap_capable in privilege check") fd2a80438d736 ("apparmor: add ns being viewed as a param to policy_admin_capable()") fe6bb31f590c9 ("apparmor: split out shared policy_XXX fns to lib") v4.4.230: Failed to apply! Possible dependencies: 078c73c63fb28 ("apparmor: add profile and ns params to aa_may_manage_policy()") 121d4a91e3c12 ("apparmor: rename sid to secid") 12557dcba21b0 ("apparmor: move lib definitions into separate lib include") 2bd8dbbf22fe9 ("apparmor: add ns being viewed as a param to policy_view_capable()") 5ac8c355ae001 ("apparmor: allow introspecting the loaded policy pre internal transform") 637f688dc3dc3 ("apparmor: switch from profiles to using labels on contexts") 73688d1ed0b8f ("apparmor: refactor prepare_ns() and make usable from different views") 79be093500791 ("Smack: File receive for sockets") 9481769208b5e ("->file_open(): lose cred argument") 98849dff90e27 ("apparmor: rename namespace to ns to improve code line lengths") 9a2d40c12d00e ("apparmor: add strn version of aa_find_ns") a6f233003b1af ("apparmor: allow specifying the profile doing the management") b17103a8b8ae9 ("Smack: Abstract use of cred security blob") c60b906673eeb ("Smack: Signal delivery as an append operation") cff281f6861e7 ("apparmor: split apparmor policy namespaces code into its own file") d19dfe58b7ecb ("Smack: Privilege check on key operations") dcb569cf6ac99 ("Smack: ptrace capability use fixes") f28e783ff668c ("Smack: Use cap_capable in privilege check") fd2a80438d736 ("apparmor: add ns being viewed as a param to policy_admin_capable()") fe6bb31f590c9 ("apparmor: split out shared policy_XXX fns to lib") NOTE: The patch will not be queued to stable trees until it is upstream. How should we proceed with this patch? -- Thanks Sasha ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Smack: fix use-after-free in smk_write_relabel_self() 2020-07-08 20:15 ` [PATCH] Smack: fix use-after-free in smk_write_relabel_self() Eric Biggers 2020-07-16 0:27 ` Sasha Levin @ 2020-07-21 0:38 ` Eric Biggers 2020-07-21 0:57 ` Casey Schaufler 1 sibling, 1 reply; 5+ messages in thread From: Eric Biggers @ 2020-07-21 0:38 UTC (permalink / raw) To: linux-security-module, Casey Schaufler, James Morris, Serge E . Hallyn Cc: syzkaller-bugs, linux-kernel, stable, syzbot+e6416dabb497a650da40 On Wed, Jul 08, 2020 at 01:15:20PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > smk_write_relabel_self() frees memory from the task's credentials with > no locking, which can easily cause a use-after-free because multiple > tasks can share the same credentials structure. > > Fix this by using prepare_creds() and commit_creds() to correctly modify > the task's credentials. > > Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self": > > #include <fcntl.h> > #include <pthread.h> > #include <unistd.h> > > static void *thrproc(void *arg) > { > int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY); > for (;;) write(fd, "foo", 3); > } > > int main() > { > pthread_t t; > pthread_create(&t, NULL, thrproc, NULL); > thrproc(NULL); > } > > Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com > Fixes: 38416e53936e ("Smack: limited capability for changing process label") > Cc: <stable@vger.kernel.org> # v4.4+ > Signed-off-by: Eric Biggers <ebiggers@google.com> Ping. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Smack: fix use-after-free in smk_write_relabel_self() 2020-07-21 0:38 ` Eric Biggers @ 2020-07-21 0:57 ` Casey Schaufler 0 siblings, 0 replies; 5+ messages in thread From: Casey Schaufler @ 2020-07-21 0:57 UTC (permalink / raw) To: Eric Biggers, linux-security-module, James Morris, Serge E . Hallyn Cc: syzkaller-bugs, linux-kernel, stable, syzbot+e6416dabb497a650da40, Casey Schaufler On 7/20/2020 5:38 PM, Eric Biggers wrote: > On Wed, Jul 08, 2020 at 01:15:20PM -0700, Eric Biggers wrote: >> From: Eric Biggers <ebiggers@google.com> >> >> smk_write_relabel_self() frees memory from the task's credentials with >> no locking, which can easily cause a use-after-free because multiple >> tasks can share the same credentials structure. >> >> Fix this by using prepare_creds() and commit_creds() to correctly modify >> the task's credentials. >> >> Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self": >> >> #include <fcntl.h> >> #include <pthread.h> >> #include <unistd.h> >> >> static void *thrproc(void *arg) >> { >> int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY); >> for (;;) write(fd, "foo", 3); >> } >> >> int main() >> { >> pthread_t t; >> pthread_create(&t, NULL, thrproc, NULL); >> thrproc(NULL); >> } >> >> Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com >> Fixes: 38416e53936e ("Smack: limited capability for changing process label") >> Cc: <stable@vger.kernel.org> # v4.4+ >> Signed-off-by: Eric Biggers <ebiggers@google.com> > Ping. I have queued your patch and will be pushing it for next shortly. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-07-21 0:57 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-06-08 21:56 KASAN: use-after-free Read in smk_write_relabel_self syzbot 2020-07-08 20:15 ` [PATCH] Smack: fix use-after-free in smk_write_relabel_self() Eric Biggers 2020-07-16 0:27 ` Sasha Levin 2020-07-21 0:38 ` Eric Biggers 2020-07-21 0:57 ` Casey Schaufler
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