Le 29/03/2022 à 13:20, Christian Brauner a écrit :
On Sun, Mar 27, 2022 at 01:18:17PM +0200, Christophe JAILLET wrote:
ida_alloc_max(..., max, ...) returns values from 0 to max, inclusive.
So, BINDERFS_MAX_MINOR is a valid value for 'minor'.
BINDERFS_MAX_MINOR is '1U << MINORBITS' and we have:
#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
So, When this value is used in MKDEV() and it will overflow.
Fixes: 3ad20fe393b3 ("binder: implement binderfs")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
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This patch is completely speculative.
The 'BINDERFS_MAX_MINOR_CAPPED - 1' is here only for symmetry with the
BINDERFS_MAX_MINOR case. I'm not sure at all that is is needed and, more
importantly, that it is correct.
Hm, since we're "removing" one alloctable device for the initial ipc
namespace, I think we need the -1 for the capped value.
Though I wonder if the simpler fix wouldn't just be to:
#define BINDERFS_MAX_MINOR MINORMASK
since include/linux/kdev_t.h has:
#define MINORBITS 20
#define MINORMASK ((1U << MINORBITS) - 1)
Hi,
I mostly agree with you, but I don't have a strong opinion on the other
uses of BINDERFS_MAX_MINOR.
The ones related to 'max' values looks good to me, but I don't know the
implication for the one used in binderfs_make_inode() and in
init_binderfs().
I won't be able to help further here.
CJ
