Message ID | 20221017063406.604188-1-cuigaosheng1@huawei.com |
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State | New |
Headers |
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Series |
copy_process(): fix a memleak in copy_process()
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Commit Message
Gaosheng Cui
Oct. 17, 2022, 6:34 a.m. UTC
If CLONE_PIDFD is set in clone_flags, pidfile will hold the reference
count of pid by getpid(pid), In the error path bad_fork_put_pidfd, the
reference of pid needs to be released, otherwise there will be a
memleak issue, fix it.
unreferenced object 0xffff888164aed400 (size 224):
comm "sh", pid 75274, jiffies 4295717290 (age 2955.536s)
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de .............N..
ff ff ff ff 00 00 00 00 ff ff ff ff ff ff ff ff ................
backtrace:
[<00000000bcb9eebb>] kmem_cache_alloc+0x16a/0x7f0
[<00000000340cf9ad>] alloc_pid+0xc5/0xce0
[<000000002387362c>] copy_process+0x29ef/0x6c90
[<00000000bf7d7efc>] kernel_clone+0xd9/0xc70
[<0000000047b1a04f>] __do_sys_clone+0xe1/0x120
[<0000000000f1aa25>] __x64_sys_clone+0xc3/0x150
[<00000000250a19f1>] do_syscall_64+0x5c/0x90
[<000000007e0ac417>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
---
kernel/fork.c | 1 +
1 file changed, 1 insertion(+)
Comments
On Mon, Oct 17, 2022 at 02:34:06PM +0800, Gaosheng Cui wrote: > If CLONE_PIDFD is set in clone_flags, pidfile will hold the reference > count of pid by getpid(pid), In the error path bad_fork_put_pidfd, the > reference of pid needs to be released, otherwise there will be a > memleak issue, fix it. > > unreferenced object 0xffff888164aed400 (size 224): > comm "sh", pid 75274, jiffies 4295717290 (age 2955.536s) > hex dump (first 32 bytes): > 01 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de .............N.. > ff ff ff ff 00 00 00 00 ff ff ff ff ff ff ff ff ................ > backtrace: > [<00000000bcb9eebb>] kmem_cache_alloc+0x16a/0x7f0 > [<00000000340cf9ad>] alloc_pid+0xc5/0xce0 > [<000000002387362c>] copy_process+0x29ef/0x6c90 > [<00000000bf7d7efc>] kernel_clone+0xd9/0xc70 > [<0000000047b1a04f>] __do_sys_clone+0xe1/0x120 > [<0000000000f1aa25>] __x64_sys_clone+0xc3/0x150 > [<00000000250a19f1>] do_syscall_64+0x5c/0x90 > [<000000007e0ac417>] entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups") > Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com> > --- > kernel/fork.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 08969f5aa38d..8706c06be8af 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -2499,6 +2499,7 @@ static __latent_entropy struct task_struct *copy_process( > cgroup_cancel_fork(p, args); > bad_fork_put_pidfd: > if (clone_flags & CLONE_PIDFD) { > + put_pid(pid); This will be released during __fput() when ->release() == pidfd_release() is called so calling put_pid() here will result in UAF later on. What syzbot instance does this report come from?
> This will be released during __fput() when ->release() == > pidfd_release() is called so calling put_pid() here will result in UAF > later on. What syzbot instance does this report come from? > . Thanks for taking time to review the patch, kmemleak report this when I'm doing some kernel tests, unfortunately, I didn't realize that pidfd_release would release pid. Perhaps there is another reason for this issue, but I'm not sure now, I will try to prove it. By the way, do you have any ideas about it? such as "->release() == NULL"? Thanks very much! On 2022/10/17 15:18, Christian Brauner wrote: > On Mon, Oct 17, 2022 at 02:34:06PM +0800, Gaosheng Cui wrote: >> If CLONE_PIDFD is set in clone_flags, pidfile will hold the reference >> count of pid by getpid(pid), In the error path bad_fork_put_pidfd, the >> reference of pid needs to be released, otherwise there will be a >> memleak issue, fix it. >> >> unreferenced object 0xffff888164aed400 (size 224): >> comm "sh", pid 75274, jiffies 4295717290 (age 2955.536s) >> hex dump (first 32 bytes): >> 01 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de .............N.. >> ff ff ff ff 00 00 00 00 ff ff ff ff ff ff ff ff ................ >> backtrace: >> [<00000000bcb9eebb>] kmem_cache_alloc+0x16a/0x7f0 >> [<00000000340cf9ad>] alloc_pid+0xc5/0xce0 >> [<000000002387362c>] copy_process+0x29ef/0x6c90 >> [<00000000bf7d7efc>] kernel_clone+0xd9/0xc70 >> [<0000000047b1a04f>] __do_sys_clone+0xe1/0x120 >> [<0000000000f1aa25>] __x64_sys_clone+0xc3/0x150 >> [<00000000250a19f1>] do_syscall_64+0x5c/0x90 >> [<000000007e0ac417>] entry_SYSCALL_64_after_hwframe+0x63/0xcd >> >> Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups") >> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com> >> --- >> kernel/fork.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/kernel/fork.c b/kernel/fork.c >> index 08969f5aa38d..8706c06be8af 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -2499,6 +2499,7 @@ static __latent_entropy struct task_struct *copy_process( >> cgroup_cancel_fork(p, args); >> bad_fork_put_pidfd: >> if (clone_flags & CLONE_PIDFD) { >> + put_pid(pid); > This will be released during __fput() when ->release() == > pidfd_release() is called so calling put_pid() here will result in UAF > later on. What syzbot instance does this report come from? > .
diff --git a/kernel/fork.c b/kernel/fork.c index 08969f5aa38d..8706c06be8af 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2499,6 +2499,7 @@ static __latent_entropy struct task_struct *copy_process( cgroup_cancel_fork(p, args); bad_fork_put_pidfd: if (clone_flags & CLONE_PIDFD) { + put_pid(pid); fput(pidfile); put_unused_fd(pidfd); }