On Sun, Jan 07, 2024 at 03:05:59PM +0800, Su Yue wrote:
> The pointer dev_name can be modified by strseq(),
> then causes the memleak:
>
> unreferenced object 0xffff9d08a2916c80 (size 32):
> comm "mount.bcachefs", pid 9090, jiffies 4295856224 (age 17.564s)
> hex dump (first 32 bytes):
> 2f 64 65 76 2f 6d 61 70 70 65 72 2f 74 65 73 74 /dev/mapper/test
> 2d 30 00 00 00 00 00 00 00 00 00 00 00 00 00 00 -0..............
> backtrace:
> [<00000000c5d3be7d>] __kmem_cache_alloc_node+0x1f3/0x2c0
> [<0000000052215d26>] __kmalloc_node_track_caller+0x51/0x150
> [<0000000069fea956>] kstrdup+0x32/0x60
> [<000000000877fcf1>] bch2_split_devs+0x3f/0x150 [bcachefs]
> [<000000007ee93204>] bch2_mount+0xcb/0x640 [bcachefs]
> [<000000002dd1e04b>] legacy_get_tree+0x30/0x60
> [<000000006afc31d3>] vfs_get_tree+0x28/0xf0
> [<000000007b0c538e>] path_mount+0x475/0xb60
> [<0000000092de5882>] __x64_sys_mount+0x105/0x140
> [<0000000054fc05d8>] do_syscall_64+0x42/0xf0
> [<00000000df584910>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
>
> Fix it by copying pointer dev_name at beginning then freeing the copied
> pointer at end.
>
> Signed-off-by: Su Yue <[email protected]>
> ---
> fs/bcachefs/util.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c
> index c2ef7cddaa4f..789953c14f55 100644
> --- a/fs/bcachefs/util.c
> +++ b/fs/bcachefs/util.c
> @@ -1186,7 +1186,9 @@ int bch2_split_devs(const char *_dev_name, darray_str
> *ret)
> {
> darray_init(ret);
>
> - char *dev_name = kstrdup(_dev_name, GFP_KERNEL), *s = dev_name;
> + char *dev_name = kstrdup(_dev_name, GFP_KERNEL);
> + char *s = dev_name, *orig = dev_name;
> +
Thanks for the patch. I see this is just moving the assignment of *s,
but there's no need for that assignment in this code, right? If not, I
think this would look a little bit cleaner if it fixed that up as well.
I.e., something like:
char *s, *dev_name, *orig;
dev_name = orig = kstrdup(_dev_name, GFP_KERNEL);
> if (!dev_name)
> return -ENOMEM;
>
... and then otherwise the rest LGTM.
Brian
> @@ -1201,10 +1203,10 @@ int bch2_split_devs(const char *_dev_name, darray_str
> *ret)
> }
> }
>
> - kfree(dev_name);
> + kfree(orig);
> return 0;
> err:
> bch2_darray_str_exit(ret);
> - kfree(dev_name);
> + kfree(orig);
> return -ENOMEM;
> }
> --
> 2.43.0
>
>
