user/sven/linux.git/fs, branch v4.4.295

tracefs: Set all files to the same group ownership as the mount option

2021-12-14T09:03:49Z

commit 48b27b6b5191e2e1f2798cd80877b6e4ef47c351 upstream. As people have been asking to allow non-root processes to have access to the tracefs directory, it was considered best to only allow groups to have access to the directory, where it is easier to just set the tracefs file system to a specific group (as other would be too dangerous), and that way the admins could pick which processes would have access to tracefs. Unfortunately, this broke tooling on Android that expected the other bit to be set. For some special cases, for non-root tools to trace the system, tracefs would be mounted and change the permissions of the top level directory which gave access to all running tasks permission to the tracing directory. Even though this would be dangerous to do in a production environment, for testing environments this can be useful. Now with the new changes to not allow other (which is still the proper thing to do), it breaks the testing tooling. Now more code needs to be loaded on the system to change ownership of the tracing directory. The real solution is to have tracefs honor the gid=xxx option when mounting. That is, (tracing group tracing has value 1003) mount -t tracefs -o gid=1003 tracefs /sys/kernel/tracing should have it that all files in the tracing directory should be of the given group. Copy the logic from d_walk() from dcache.c and simplify it for the mount case of tracefs if gid is set. All the files in tracefs will be walked and their group will be set to the value passed in. Link: https://lkml.kernel.org/r/20211207171729.2a54e1b3@gandalf.local.home Cc: Ingo Molnar Cc: Kees Cook Cc: Andrew Morton Cc: Linus Torvalds Cc: linux-fsdevel@vger.kernel.org Cc: Al Viro Cc: Greg Kroah-Hartman Reported-by: Kalesh Singh Reported-by: Yabin Cui Fixes: 49d67e445742 ("tracefs: Have tracefs directories not set OTH permission bits by default") Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman

signalfd: use wake_up_pollfree()

2021-12-14T09:03:49Z

commit 9537bae0da1f8d1e2361ab6d0479e8af7824e160 upstream. wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up all exclusive waiters. Yet, POLLFREE *must* wake up all waiters. epoll and aio poll are fortunately not affected by this, but it's very fragile. Thus, the new function wake_up_pollfree() has been introduced. Convert signalfd to use wake_up_pollfree(). Reported-by: Linus Torvalds Fixes: d80e731ecab4 ("epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211209010455.42744-4-ebiggers@kernel.org Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman

tracefs: Have new files inherit the ownership of their parent

2021-12-14T09:03:49Z

commit ee7f3666995d8537dec17b1d35425f28877671a9 upstream. If directories in tracefs have their ownership changed, then any new files and directories that are created under those directories should inherit the ownership of the director they are created in. Link: https://lkml.kernel.org/r/20211208075720.4855d180@gandalf.local.home Cc: Kees Cook Cc: Ingo Molnar Cc: Andrew Morton Cc: Linus Torvalds Cc: Al Viro Cc: Greg Kroah-Hartman Cc: Yabin Cui Cc: Christian Brauner Cc: stable@vger.kernel.org Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system") Reported-by: Kalesh Singh Reported: https://lore.kernel.org/all/CAC_TJve8MMAv+H_NdLSJXZUSoxOEq2zB_pVaJ9p=7H6Bu3X76g@mail.gmail.com/ Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman

fget: check that the fd still exists after getting a ref to it

2021-12-08T07:44:08Z

commit 054aa8d439b9185d4f5eb9a90282d1ce74772969 upstream. Jann Horn points out that there is another possible race wrt Unix domain socket garbage collection, somewhat reminiscent of the one fixed in commit cbcf01128d0a ("af_unix: fix garbage collect vs MSG_PEEK"). See the extended comment about the garbage collection requirements added to unix_peek_fds() by that commit for details. The race comes from how we can locklessly look up a file descriptor just as it is in the process of being closed, and with the right artificial timing (Jann added a few strategic 'mdelay(500)' calls to do that), the Unix domain socket garbage collector could see the reference count decrement of the close() happen before fget() took its reference to the file and the file was attached onto a new file descriptor. This is all (intentionally) correct on the 'struct file *' side, with RCU lookups and lockless reference counting very much part of the design. Getting that reference count out of order isn't a problem per se. But the garbage collector can get confused by seeing this situation of having seen a file not having any remaining external references and then seeing it being attached to an fd. In commit cbcf01128d0a ("af_unix: fix garbage collect vs MSG_PEEK") the fix was to serialize the file descriptor install with the garbage collector by taking and releasing the unix_gc_lock. That's not really an option here, but since this all happens when we are in the process of looking up a file descriptor, we can instead simply just re-check that the file hasn't been closed in the meantime, and just re-do the lookup if we raced with a concurrent close() of the same file descriptor. Reported-and-tested-by: Jann Horn Acked-by: Miklos Szeredi Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

fs: add fget_many() and fput_many()

2021-12-08T07:44:08Z

commit 091141a42e15fe47ada737f3996b317072afcefb upstream. Some uses cases repeatedly get and put references to the same file, but the only exposed interface is doing these one at the time. As each of these entail an atomic inc or dec on a shared structure, that cost can add up. Add fget_many(), which works just like fget(), except it takes an argument for how many references to get on the file. Ditto fput_many(), which can drop an arbitrary number of references to a file. Reviewed-by: Hannes Reinecke Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

fuse: release pipe buf after last use

2021-12-08T07:44:06Z

commit 473441720c8616dfaf4451f9c7ea14f0eb5e5d65 upstream. Checking buf->flags should be done before the pipe_buf_release() is called on the pipe buffer, since releasing the buffer might modify the flags. This is exactly what page_cache_pipe_buf_release() does, and which results in the same VM_BUG_ON_PAGE(PageLRU(page)) that the original patch was trying to fix. Reported-by: Justin Forbes Fixes: 712a951025c0 ("fuse: fix page stealing") Cc: # v2.6.35 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: fix page stealing

2021-12-08T07:44:06Z

commit 712a951025c0667ff00b25afc360f74e639dfabe upstream. It is possible to trigger a crash by splicing anon pipe bufs to the fuse device. The reason for this is that anon_pipe_buf_release() will reuse buf->page if the refcount is 1, but that page might have already been stolen and its flags modified (e.g. PG_lru added). This happens in the unlikely case of fuse_dev_splice_write() getting around to calling pipe_buf_release() after a page has been stolen, added to the page cache and removed from the page cache. Fix by calling pipe_buf_release() right after the page was inserted into the page cache. In this case the page has an elevated refcount so any release function will know that the page isn't reusable. Reported-by: Frank Dinoff Link: https://lore.kernel.org/r/CAAmZXrsGg2xsP1CK+cbuEMumtrqdvD-NKnWzhNcvn71RV3c1yw@mail.gmail.com/ Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device") Cc: # v2.6.35 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

proc/vmcore: fix clearing user buffer by properly using clear_user()

2021-12-08T07:44:06Z

commit c1e63117711977cc4295b2ce73de29dd17066c82 upstream. To clear a user buffer we cannot simply use memset, we have to use clear_user(). With a virtio-mem device that registers a vmcore_cb and has some logically unplugged memory inside an added Linux memory block, I can easily trigger a BUG by copying the vmcore via "cp": systemd[1]: Starting Kdump Vmcore Save Service... kdump[420]: Kdump is using the default log level(3). kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[465]: saving vmcore-dmesg.txt complete kdump[467]: saving vmcore BUG: unable to handle page fault for address: 00007f2374e01000 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Oops: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86 Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81 RSP: 0018:ffffc9000073be08 EFLAGS: 00010212 RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000 RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008 RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Call Trace: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 ksys_read+0x4f/0xc0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access Prevention (SMAP)", which is used to detect wrong access from the kernel to user buffers like this: SMAP triggers a permissions violation on wrong access. In the x86-64 variant of clear_user(), SMAP is properly handled via clac()+stac(). To fix, properly use clear_user() when we're dealing with a user buffer. Link: https://lkml.kernel.org/r/20211112092750.6921-1-david@redhat.com Fixes: 997c136f518c ("fs/proc/vmcore.c: add hook to read_from_oldmem() to check for non-ram pages") Signed-off-by: David Hildenbrand Acked-by: Baoquan He Cc: Dave Young Cc: Baoquan He Cc: Vivek Goyal Cc: Philipp Rudo Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

NFSv42: Don't fail clone() unless the OP_CLONE operation failed

2021-12-08T07:44:05Z

[ Upstream commit d3c45824ad65aebf765fcf51366d317a29538820 ] The failure to retrieve post-op attributes has no bearing on whether or not the clone operation itself was successful. We must therefore ignore the return value of decode_getfattr() when looking at the success or failure of nfs4_xdr_dec_clone(). Fixes: 36022770de6c ("nfs42: add CLONE xdr functions") Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin

btrfs: fix memory ordering between normal and ordered work functions

2021-11-26T10:58:44Z

commit 45da9c1767ac31857df572f0a909fbe88fd5a7e9 upstream. Ordered work functions aren't guaranteed to be handled by the same thread which executed the normal work functions. The only way execution between normal/ordered functions is synchronized is via the WORK_DONE_BIT, unfortunately the used bitops don't guarantee any ordering whatsoever. This manifested as seemingly inexplicable crashes on ARM64, where async_chunk::inode is seen as non-null in async_cow_submit which causes submit_compressed_extents to be called and crash occurs because async_chunk::inode suddenly became NULL. The call trace was similar to: pc : submit_compressed_extents+0x38/0x3d0 lr : async_cow_submit+0x50/0xd0 sp : ffff800015d4bc20 Call trace: submit_compressed_extents+0x38/0x3d0 async_cow_submit+0x50/0xd0 run_ordered_work+0xc8/0x280 btrfs_work_helper+0x98/0x250 process_one_work+0x1f0/0x4ac worker_thread+0x188/0x504 kthread+0x110/0x114 ret_from_fork+0x10/0x18 Fix this by adding respective barrier calls which ensure that all accesses preceding setting of WORK_DONE_BIT are strictly ordered before setting the flag. At the same time add a read barrier after reading of WORK_DONE_BIT in run_ordered_work which ensures all subsequent loads would be strictly ordered after reading the bit. This in turn ensures are all accesses before WORK_DONE_BIT are going to be strictly ordered before any access that can occur in ordered_func. Reported-by: Chris Murphy Fixes: 08a9ff326418 ("btrfs: Added btrfs_workqueue_struct implemented ordered execution based on kernel workqueue") CC: stable@vger.kernel.org # 4.4+ Link: https://bugzilla.redhat.com/show_bug.cgi?id=2011928 Reviewed-by: Josef Bacik Tested-by: Chris Murphy Signed-off-by: Nikolay Borisov Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman