Messages in this thread | | | Date | Tue, 3 Nov 2020 18:29:08 -0800 | From | Eric Biggers <> | Subject | Re: [f2fs-dev] [PATCH RFC] f2fs: fix compat F2FS_IOC_{MOVE, GARBAGE_COLLECT}_RANGE |
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On Wed, Nov 04, 2020 at 10:19:06AM +0800, Chao Yu wrote: > Eric reported a ioctl bug in below link: > > https://lore.kernel.org/linux-f2fs-devel/20201103032234.GB2875@sol.localdomain/ > > That said, on some 32-bit architectures, u64 has only 32-bit alignment, > notably i386 and x86_32, so that size of struct f2fs_gc_range compiled > in x86_32 is 20 bytes, however the size in x86_64 is 24 bytes, binary > compiled in x86_32 can not call F2FS_IOC_GARBAGE_COLLECT_RANGE successfully > due to mismatched value of ioctl command in betweeen binary and f2fs > module, similarly, F2FS_IOC_MOVE_RANGE will fail too. > > In this patch we introduce two ioctls for compatibility of above special > 32-bit binary: > - F2FS_IOC32_GARBAGE_COLLECT_RANGE > - F2FS_IOC32_MOVE_RANGE > > Signed-off-by: Chao Yu <yuchao0@huawei.com> > --- > > Jaegeuk, Eric, > > I have no 32-bit machine now, so I don't run any test on this patch, > please take a look at this RFC patch first.
You can test this by running a 32-bit binary on a machine with a 64-bit kernel. E.g. on x86_64, compile a binary with 'gcc -m32'.
> #ifdef CONFIG_COMPAT > +static int f2fs_compat_ioc_gc_range(struct file *file, unsigned long arg) > +{ > + struct compat_f2fs_gc_range __user *urange; > + struct f2fs_gc_range range; > + int err; > + > + urange = compat_ptr(arg); > + err = get_user(range.sync, &urange->sync); > + err |= get_user(range.start, &urange->start); > + err |= get_user(range.len, &urange->len); > + if (err) > + return -EFAULT; > + if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(file))))) > + return -EIO; > + if (!f2fs_is_checkpoint_ready(F2FS_I_SB(file_inode(file)))) > + return -ENOSPC; > + return f2fs_ioc_gc_range(file, (unsigned long)&range); > +}
This won't work because f2fs_ioc_gc_range() expects a user pointer. You'll need to make the native and compat versions do the copy from user separately, and have them call a helper function that takes a pointer to the argument in kernel memory.
- Eric
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