From: Linus Torvalds torvalds@linux-foundation.org
[ Upstream commit d888c83fcec75194a8a48ccd283953bdba7b2550 ]
Jason Donenfeld reports that my commit 1c24a186398f ("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: 1c24a186398f ("fs: fd tables have to be multiples of BITS_PER_LONG") Reported-and-tested-by: Jason 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: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/file.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/file.c b/fs/file.c index c01c29417ae6..ee9317346702 100644 --- a/fs/file.c +++ b/fs/file.c @@ -303,10 +303,9 @@ 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); }
/*