Messages in this thread | | | From | Dongliang Mu <> | Date | Fri, 12 Aug 2022 22:02:36 +0800 | Subject | Re: [PATCH] drivers: binderfs: fix memory leak in binderfs_fill_super |
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On Fri, Aug 12, 2022 at 9:56 PM Dongliang Mu <mudongliangabcd@gmail.com> wrote: > > On Fri, Aug 12, 2022 at 9:41 PM Greg Kroah-Hartman > <gregkh@linuxfoundation.org> wrote: > > > > On Fri, Aug 12, 2022 at 09:21:24PM +0800, Dongliang Mu wrote: > > > From: Dongliang Mu <mudongliangabcd@gmail.com> > > > > > > In binderfs_fill_super, if s_root is not successfully initialized by > > > d_make_root, the previous allocated s_sb_info will not be freed since > > > generic_shutdown_super first checks if sb->s_root and then does > > > put_super operation. The put_super operation calls binderfs_put_super > > > to deallocate s_sb_info and put ipc_ns. This will lead to memory leak > > > in binderfs_fill_super. > > > > > > Fix this by invoking binderfs_put_super at error sites before s_root > > > is successfully initialized. > > > > > > Fixes: 095cf502b31e ("binderfs: port to new mount api") > > > Reported-by: syzkaller <syzkaller@googlegroups.com> > > > > Where is the specific syzkaller link for this report? It would be good > > to reference it so it can be properly checked. > > > > Also, how did you test this change? > > I found this memory leak in my local syzkaller, and there is no any > syzbot report about this crash, therefore I use such a Reported-by to > indicate. > > Although my local syzkaller does generate any reproducer, this bug can > be triggered by injecting faults at new_inode and d_make_root (i.e., > between s_sb_info allocation and code after d_make_root). > > > > > > Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com> > > > --- > > > drivers/android/binderfs.c | 8 ++++++-- > > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c > > > index 588d753a7a19..20f5bc77495f 100644 > > > --- a/drivers/android/binderfs.c > > > +++ b/drivers/android/binderfs.c > > > @@ -710,8 +710,10 @@ static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc) > > > info->mount_opts.stats_mode = ctx->stats_mode; > > > > > > inode = new_inode(sb); > > > - if (!inode) > > > + if (!inode) { > > > + binderfs_put_super(sb); > > > return -ENOMEM; > > > + } > > > > > > inode->i_ino = FIRST_INODE; > > > inode->i_fop = &simple_dir_operations; > > > @@ -721,8 +723,10 @@ static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc) > > > set_nlink(inode, 2); > > > > > > sb->s_root = d_make_root(inode); > > > - if (!sb->s_root) > > > + if (!sb->s_root) { > > > + binderfs_put_super(sb); > > > return -ENOMEM; > > > + } > > > > How did you test this change to verify that you are not now just leaking > > memory? It looks to me like you just changed one problem for another > > one :( > > As mentioned above, I just tested my change by injecting faults at > new_inode and d_make_root.
The following is a reproducer I extracted from syzkaller log. The fail_nth needs revision according to your own environment.
syz_mount_image$adfs(0x0, &(0x7f0000000180)='./file0\x00', 0x0, 0x0, 0x0, 0x0, 0x0) syz_mount_image$afs(0x0, &(0x7f0000000040)='./file0/file0\x00', 0x0, 0x0, 0x0, 0x0, 0x0) mount(&(0x7f0000000100)=@nbd={'/dev/nbd', 0x0}, &(0x7f0000000140)='./file0/file0\x00', &(0x7f0000000280)='binder\x00', 0x0, 0x0) (fail_nth: 40)
> > Can you explain more about "changed one problem for another one"? I > don't quite understand this statement. > > > > > Please always be very very careful when making these types of changes, > > and verify and test that they are correct. > > > > thanks, > > > > greg k-h
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