• Jiri Slaby's avatar
    hwrng: core - sleep interruptible in read · 1ab87298
    Jiri Slaby authored
    hwrng kthread can be waiting via hwrng_fillfn for some data from a rng
    like virtio-rng:
    hwrng           D ffff880093e17798     0   382      2 0x00000000
    ...
    Call Trace:
     [<ffffffff817339c6>] wait_for_completion_killable+0x96/0x210
     [<ffffffffa00aa1b7>] virtio_read+0x57/0xf0 [virtio_rng]
     [<ffffffff814f4a35>] hwrng_fillfn+0x75/0x130
     [<ffffffff810aa243>] kthread+0xf3/0x110
    
    And when some user program tries to read the /dev node in this state,
    we get:
    rngd            D ffff880093e17798     0   762      1 0x00000004
    ...
    Call Trace:
     [<ffffffff817351ac>] mutex_lock_nested+0x15c/0x3e0
     [<ffffffff814f478e>] rng_dev_read+0x6e/0x240
     [<ffffffff81231958>] __vfs_read+0x28/0xe0
     [<ffffffff81232393>] vfs_read+0x83/0x130
    
    And this is indeed unkillable. So use mutex_lock_interruptible
    instead of mutex_lock in rng_dev_read and exit immediatelly when
    interrupted. And possibly return already read data, if any (as POSIX
    allows).
    
    v2: use ERESTARTSYS instead of EINTR
    Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
    Cc: Matt Mackall <mpm@selenic.com>
    Cc: Herbert Xu <herbert@gondor.apana.org.au>
    Cc: <linux-crypto@vger.kernel.org>
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    1ab87298
core.c 12.1 KB