On Wed, Oct 17, 2018 at 12:33:22AM +0200, Christian Brauner wrote: > Currently, when writing > > echo 18446744073709551616 > /proc/sys/fs/file-max > > /proc/sys/fs/file-max will overflow and be set to 0. That quickly > crashes the system. > This commit sets the max and min value for file-max and returns -EINVAL > when a long int is exceeded. Any higher value cannot currently be used as > the percpu counters are long ints and not unsigned integers. This behavior > also aligns with other tuneables that return -EINVAL when their range is > exceeded. See e.g. [1], [2] and others. Mostly sane, but... get_max_files() users are bloody odd. The one in file-max limit reporting looks like a half-arsed attempt in "[PATCH] fix file counting". The one in af_unix.c, though... I don't remember how that check had come to be - IIRC that was a strange fallout of a thread with me, Andrea and ANK involved, circa 1999, but I don't remember details; Andrea, any memories? It might be worth reconsidering... The change in question is in 2.2.4pre6; what do we use unix_nr_socks for? We try to limit the number of PF_UNIX socks by 2 * max_files, but max_files can be huge *and* non-constant (i.e. it can decrease). What's more, unix_tot_inflight is unsigned int and max_files might exceed 2^31 just fine since "fs: allow for more than 2^31 files" back in 2010... Something's fishy there...
