Date: Mon, 21 Apr 2014 08:20:22 +0200
   From: Maxime Villard <>

   Le 21/04/2014 01:46, Taylor R Campbell a écrit :
   > In most cases of the changes you made, there is already a test for the
   > length of the data buffer.  Is this not guaranteed to be zero if data
   > is null?  It seems to me that the length test ought to suffice, and if
   > anything the null pointer test should be an assertion, not a check.

   Not at all. 'data' and 'data_len' come from userpace. A user can set data
   to NULL and data_len to a value high enough to bypass the data_len check.

If a user passes in null data and nonzero data_len, why doesn't
mount(2) just return EINVAL?

Giving file systems the responsibility for basic sanity checks on
syscall arguments strikes me as error-prone.

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