Re: Endless getdents() in vfat filesystem

From: Vegard Nossum
Date: Sun Nov 15 2015 - 06:06:48 EST

On 11/14/2015 07:19 PM, OGAWA Hirofumi wrote:
Richard Weinberger <richard@xxxxxx> writes:

Yes, it does fixes the problem here, but I can't really comment on the
correctness of the patch.

Thanks for the quick reponse,

I made cleanup and made sure fake_offset is corrected.

Richard, Signed-off-by was missed in your patch, so I added. Can you
agree to Signed-off-by?


Attached updated patch made smaller changes, and with missed Cc: stable.

Andrew, please queue this up.


It would be nice to have a proper patch description too. How about this?

For the root directory, . and .. are faked (using dir_emit_dots()) and
ctx->pos is reset from 2 to 0.

A corrupted root directory could cause fat_get_entry() to fail, but
->iterate() (fat_readdir()) reports progress to the VFS (with ctx->pos
rewound to 0), so any following calls to ->iterate() continue to return
the same entries again and again.

The result is that userspace will never see the end of the directory,
causing e.g. 'ls' to hang in a getdents() loop.


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