fs: fix fd table size alignment properly

stable inclusion
from stable-v5.10.110
commit e600b5973e808848a23eeba3fdbb9b288e5558c1
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e600b5973e808848a23eeba3fdbb9b288e5558c1

--------------------------------

[ Upstream commit d888c83f ]

Jason Donenfeld reports that my commit 1c24a186 ("fs: fd tables have
to be multiples of BITS_PER_LONG") doesn't work, and the reason is an
embarrassing brown-paper-bag bug.

Yes, we want to align the number of fds to BITS_PER_LONG, and yes, the
reason they might not be aligned is because the incoming 'max_fd'
argument might not be aligned.

But aligining the argument - while simple - will cause a "infinitely
big" maxfd (eg NR_OPEN_MAX) to just overflow to zero.  Which most
definitely isn't what we want either.

The obvious fix was always just to do the alignment last, but I had
moved it earlier just to make the patch smaller and the code look
simpler.  Duh.  It certainly made _me_ look simple.

Fixes: 1c24a186 ("fs: fd tables have to be multiples of BITS_PER_LONG")
Reported-and-tested-by: NJason A. Donenfeld <Jason@zx2c4.com>
Cc: Fedor Pchelkin <aissur0002@gmail.com>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/file.c

@@ -302,10 +302,9 @@ static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
 	unsigned int count;
 
 	count = count_open_files(fdt);
-	max_fds = ALIGN(max_fds, BITS_PER_LONG);
 	if (max_fds < NR_OPEN_DEFAULT)
 		max_fds = NR_OPEN_DEFAULT;
-	return min(count, max_fds);
+	return ALIGN(min(count, max_fds), BITS_PER_LONG);
 }
 
 /*