user/sven/linux.git/fs/select.c, branch stable/6.2.y

select: Fix indefinitely sleeping task in poll_schedule_timeout()

2022-01-11T17:03:05Z

A task can end up indefinitely sleeping in do_select() -> poll_schedule_timeout() when the following race happens: TASK1 (thread1) TASK2 TASK1 (thread2) do_select() setup poll_wqueues table with 'fd' write data to 'fd' pollwake() table->triggered = 1 closes 'fd' thread1 is waiting for poll_schedule_timeout() - sees table->triggered table->triggered = 0 return -EINTR loop back in do_select() But at this point when TASK1 loops back, the fdget() in the setup of poll_wqueues fails. So now so we never find 'fd' is ready for reading and sleep in poll_schedule_timeout() indefinitely. Treat an fd that got closed as a fd on which some event happened. This makes sure cannot block indefinitely in do_select(). Another option would be to return -EBADF in this case but that has a potential of subtly breaking applications that excercise this behavior and it happens to work for them. So returning fd as active seems like a safer choice. Suggested-by: Linus Torvalds CC: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Linus Torvalds

net: Don't include filter.h from net/sock.h

2021-12-29T16:48:14Z

sock.h is pretty heavily used (5k objects rebuilt on x86 after it's touched). We can drop the include of filter.h from it and add a forward declaration of struct sk_filter instead. This decreases the number of rebuilt objects when bpf.h is touched from ~5k to ~1k. There's a lot of missing includes this was masking. Primarily in networking tho, this time. Signed-off-by: Jakub Kicinski Signed-off-by: Alexei Starovoitov Acked-by: Marc Kleine-Budde Acked-by: Florian Fainelli Acked-by: Nikolay Aleksandrov Acked-by: Stefano Garzarella Link: https://lore.kernel.org/bpf/20211229004913.513372-1-kuba@kernel.org

Revert "memcg: enable accounting for pollfd and select bits arrays"

2021-09-07T18:26:23Z

This reverts commit b655843444152c0a14b749308e4cb35d91cbcf0b. Just like with the memcg lock accounting, the kernel test robot reports a sizeable performance regression for this commit, and while it clearly does the rigth thing in theory, we'll need to look at just how to avoid or minimize the performance overhead of the memcg accounting. People already have suggestions on how to do that, but it's "future work". So revert it for now. [ Note: the first link below is for this same commit but a different commit ID, because it's the kernel test robot ended up noticing it in Andrew Morton's patch queue ] Link: https://lore.kernel.org/lkml/20210905132732.GC15026@xsang-OptiPlex-9020/ Link: https://lore.kernel.org/lkml/20210907150757.GE17617@xsang-OptiPlex-9020/ Acked-by: Jens Axboe Acked-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Tejun Heo Signed-off-by: Linus Torvalds

memcg: enable accounting for pollfd and select bits arrays

2021-09-03T16:58:12Z

User can call select/poll system calls with a large number of assigned file descriptors and force kernel to allocate up to several pages of memory till end of these sleeping system calls. We have here long-living unaccounted per-task allocations. It makes sense to account for these allocations to restrict the host's memory consumption from inside the memcg-limited container. Link: https://lkml.kernel.org/r/56e31cb5-6e1e-bdba-d7ca-be64b9842363@virtuozzo.com Signed-off-by: Vasily Averin Reviewed-by: Shakeel Butt Cc: Alexander Viro Cc: Alexey Dobriyan Cc: Andrei Vagin Cc: Borislav Petkov Cc: Borislav Petkov Cc: Christian Brauner Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: "Eric W. Biederman" Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: "J. Bruce Fields" Cc: Jeff Layton Cc: Jens Axboe Cc: Jiri Slaby Cc: Johannes Weiner Cc: Kirill Tkhai Cc: Michal Hocko Cc: Oleg Nesterov Cc: Roman Gushchin Cc: Serge Hallyn Cc: Tejun Heo Cc: Thomas Gleixner Cc: Vladimir Davydov Cc: Yutian Yang Cc: Zefan Li Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data()

2021-03-16T21:13:10Z

Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT. Add a new helper which sets restart_block->fn and calls a dummy arch_set_restart_data() helper. Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code") Signed-off-by: Oleg Nesterov Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210201174641.GA17871@redhat.com

poll: fix performance regression due to out-of-line __put_user()

2021-01-08T19:06:29Z

The kernel test robot reported a -5.8% performance regression on the "poll2" test of will-it-scale, and bisected it to commit d55564cfc222 ("x86: Make __put_user() generate an out-of-line call"). I didn't expect an out-of-line __put_user() to matter, because no normal core code should use that non-checking legacy version of user access any more. But I had overlooked the very odd poll() usage, which does a __put_user() to update the 'revents' values of the poll array. Now, Al Viro correctly points out that instead of updating just the 'revents' field, it would be much simpler to just copy the _whole_ pollfd entry, and then we could just use "copy_to_user()" on the whole array of entries, the same way we use "copy_from_user()" a few lines earlier to get the original values. But that is not what we've traditionally done, and I worry that threaded applications might be concurrently modifying the other fields of the pollfd array. So while Al's suggestion is simpler - and perhaps worth trying in the future - this instead keeps the "just update revents" model. To fix the performance regression, use the modern "unsafe_put_user()" instead of __put_user(), with the proper "user_write_access_begin()" guarding in place. This improves code generation enormously. Link: https://lore.kernel.org/lkml/20210107134723.GA28532@xsang-OptiPlex-9020/ Reported-by: kernel test robot Tested-by: Oliver Sang Cc: Al Viro Cc: David Laight Cc: Peter Zijlstra Signed-off-by: Linus Torvalds

fs: Replace zero-length array with flexible-array member

2020-10-29T22:22:59Z

There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays Signed-off-by: Gustavo A. R. Silva

pselect6() and friends: take handling the combined 6th/7th args into helper

2020-05-29T23:10:42Z

... and use unsafe_get_user(), while we are at it. Signed-off-by: Al Viro

y2038: syscalls: change remaining timeval to __kernel_old_timeval

2019-11-15T13:38:29Z

All of the remaining syscalls that pass a timeval (gettimeofday, utime, futimesat) can trivially be changed to pass a __kernel_old_timeval instead, which has a compatible layout, but avoids ambiguity with the timeval type in user space. Acked-by: Christian Brauner Acked-by: Rafael J. Wysocki Signed-off-by: Arnd Bergmann

fs/select.c: use struct_size() in kmalloc()

2019-07-17T02:23:25Z

One of the more common cases of allocation size calculations is finding the size of a structure that has a zero-sized array at the end, along with memory for some number of elements for that array. For example: struct foo { int stuff; struct boo entry[]; }; size = sizeof(struct foo) + count * sizeof(struct boo); instance = kmalloc(size, GFP_KERNEL); Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper: instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL); Also, notice that variable size is unnecessary, hence it is removed. This code was detected with the help of Coccinelle. Link: http://lkml.kernel.org/r/20190604164226.GA13823@embeddedor Signed-off-by: Gustavo A. R. Silva Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds