diff options
| author | ChenXiaoSong <chenxiaosong2@huawei.com> | 2021-11-02 22:22:06 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-05-15 19:41:59 +0200 |
| commit | 8033f109be4a1d5b466284e8ab9119c04f2a334b (patch) | |
| tree | 3b78cf38812e008caa2855db87f868e78653120d | |
| parent | 259dfb503b8f4087898403faf0e76dcb8d232e3d (diff) | |
VFS: Fix memory leak caused by concurrently mounting fs with subtype
If two processes mount same superblock, memory leak occurs:
CPU0 | CPU1
do_new_mount | do_new_mount
fs_set_subtype | fs_set_subtype
kstrdup |
| kstrdup
memrory leak |
The following reproducer triggers the problem:
1. shell command: mount -t ntfs /dev/sda1 /mnt &
2. c program: mount("/dev/sda1", "/mnt", "fuseblk", 0, "...")
with kmemleak report being along the lines of
unreferenced object 0xffff888235f1a5c0 (size 8):
comm "mount.ntfs", pid 2860, jiffies 4295757824 (age 43.423s)
hex dump (first 8 bytes):
00 a5 f1 35 82 88 ff ff ...5....
backtrace:
[<00000000656e30cc>] __kmalloc_track_caller+0x16e/0x430
[<000000008e591727>] kstrdup+0x3e/0x90
[<000000008430d12b>] do_mount.cold+0x7b/0xd9
[<0000000078d639cd>] ksys_mount+0xb2/0x150
[<000000006015988d>] __x64_sys_mount+0x29/0x40
[<00000000e0a7c118>] do_syscall_64+0xc1/0x1d0
[<00000000bcea7df5>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[<00000000803a4067>] 0xffffffffffffffff
Linus's tree already have refactoring patchset [1], one of them can fix this bug:
c30da2e981a7 ("fuse: convert to use the new mount API")
After refactoring, init super_block->s_subtype in fuse_fill_super.
Since we did not merge the refactoring patchset in this branch, I create this patch.
This patch fix this by adding a write lock while calling fs_set_subtype.
[1] https://patchwork.kernel.org/project/linux-fsdevel/patch/20190903113640.7984-3-mszeredi@redhat.com/
Fixes: 79c0b2df79eb ("add filesystem subtype support")
Cc: David Howells <dhowells@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/namespace.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 2f3c6a0350a8..396ff1bcfdad 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2490,9 +2490,12 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags, return -ENODEV; mnt = vfs_kern_mount(type, sb_flags, name, data); - if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && - !mnt->mnt_sb->s_subtype) - mnt = fs_set_subtype(mnt, fstype); + if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE)) { + down_write(&mnt->mnt_sb->s_umount); + if (!mnt->mnt_sb->s_subtype) + mnt = fs_set_subtype(mnt, fstype); + up_write(&mnt->mnt_sb->s_umount); + } put_filesystem(type); if (IS_ERR(mnt)) |