From: Alexey Gladkov legion@kernel.org
[ Upstream commit bbb6d0f3e1feb43d663af089c7dedb23be6a04fb ]
We need to increment the ucounts reference counter befor security_prepare_creds() because this function may fail and abort_creds() will try to decrement this reference.
[ 96.465056][ T8641] FAULT_INJECTION: forcing a failure. [ 96.465056][ T8641] name fail_page_alloc, interval 1, probability 0, space 0, times 0 [ 96.478453][ T8641] CPU: 1 PID: 8641 Comm: syz-executor668 Not tainted 5.14.0-rc6-syzkaller #0 [ 96.487215][ T8641] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 96.497254][ T8641] Call Trace: [ 96.500517][ T8641] dump_stack_lvl+0x1d3/0x29f [ 96.505758][ T8641] ? show_regs_print_info+0x12/0x12 [ 96.510944][ T8641] ? log_buf_vmcoreinfo_setup+0x498/0x498 [ 96.516652][ T8641] should_fail+0x384/0x4b0 [ 96.521141][ T8641] prepare_alloc_pages+0x1d1/0x5a0 [ 96.526236][ T8641] __alloc_pages+0x14d/0x5f0 [ 96.530808][ T8641] ? __rmqueue_pcplist+0x2030/0x2030 [ 96.536073][ T8641] ? lockdep_hardirqs_on_prepare+0x3e2/0x750 [ 96.542056][ T8641] ? alloc_pages+0x3f3/0x500 [ 96.546635][ T8641] allocate_slab+0xf1/0x540 [ 96.551120][ T8641] ___slab_alloc+0x1cf/0x350 [ 96.555689][ T8641] ? kzalloc+0x1d/0x30 [ 96.559740][ T8641] __kmalloc+0x2e7/0x390 [ 96.563980][ T8641] ? kzalloc+0x1d/0x30 [ 96.568029][ T8641] kzalloc+0x1d/0x30 [ 96.571903][ T8641] security_prepare_creds+0x46/0x220 [ 96.577174][ T8641] prepare_creds+0x411/0x640 [ 96.581747][ T8641] __sys_setfsuid+0xe2/0x3a0 [ 96.586333][ T8641] do_syscall_64+0x3d/0xb0 [ 96.590739][ T8641] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 96.596611][ T8641] RIP: 0033:0x445a69 [ 96.600483][ T8641] Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 [ 96.620152][ T8641] RSP: 002b:00007f1054173318 EFLAGS: 00000246 ORIG_RAX: 000000000000007a [ 96.628543][ T8641] RAX: ffffffffffffffda RBX: 00000000004ca4c8 RCX: 0000000000445a69 [ 96.636600][ T8641] RDX: 0000000000000010 RSI: 00007f10541732f0 RDI: 0000000000000000 [ 96.644550][ T8641] RBP: 00000000004ca4c0 R08: 0000000000000001 R09: 0000000000000000 [ 96.652500][ T8641] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004ca4cc [ 96.660631][ T8641] R13: 00007fffffe0b62f R14: 00007f1054173400 R15: 0000000000022000
Fixes: 905ae01c4ae2 ("Add a reference to ucounts for each cred") Reported-by: syzbot+01985d7909f9468f013c@syzkaller.appspotmail.com Signed-off-by: Alexey Gladkov legion@kernel.org Link: https://lkml.kernel.org/r/97433b1742c3331f02ad92de5a4f07d673c90613.162973535... Signed-off-by: Eric W. Biederman ebiederm@xmission.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/cred.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/cred.c b/kernel/cred.c index 098213d4a39c..8c0983fa794a 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -286,13 +286,13 @@ struct cred *prepare_creds(void) new->security = NULL; #endif
- if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) - goto error; - new->ucounts = get_ucounts(new->ucounts); if (!new->ucounts) goto error;
+ if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + goto error; + validate_creds(new); return new;
@@ -753,13 +753,13 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon) #ifdef CONFIG_SECURITY new->security = NULL; #endif - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) - goto error; - new->ucounts = get_ucounts(new->ucounts); if (!new->ucounts) goto error;
+ if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + goto error; + put_cred(old); validate_creds(new); return new;