4.9-stable review patch. If anyone has any objections, please let me know.
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From: Omar Sandoval osandov@fb.com
commit fd4e994bd1f9dc9628e168a7f619bf69f6984635 upstream.
If we have invalid flags set, when we error out we must drop our writer counter and free the buffer we allocated for the arguments. This bug is trivially reproduced with the following program on 4.7+:
#include <fcntl.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/ioctl.h> #include <sys/stat.h> #include <sys/types.h> #include <linux/btrfs.h> #include <linux/btrfs_tree.h>
int main(int argc, char **argv) { struct btrfs_ioctl_vol_args_v2 vol_args = { .flags = UINT64_MAX, }; int ret; int fd;
if (argc != 2) { fprintf(stderr, "usage: %s PATH\n", argv[0]); return EXIT_FAILURE; }
fd = open(argv[1], O_WRONLY); if (fd == -1) { perror("open"); return EXIT_FAILURE; }
ret = ioctl(fd, BTRFS_IOC_RM_DEV_V2, &vol_args); if (ret == -1) perror("ioctl");
close(fd); return EXIT_SUCCESS; }
When unmounting the filesystem, we'll hit the WARN_ON(mnt_get_writers(mnt)) in cleanup_mnt() and also may prevent the filesystem to be remounted read-only as the writer count will stay lifted.
Fixes: 6b526ed70cf1 ("btrfs: introduce device delete by devid") CC: stable@vger.kernel.org # 4.9+ Signed-off-by: Omar Sandoval osandov@fb.com Reviewed-by: Su Yue suy.fnst@cn.fujitsu.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/ioctl.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2708,8 +2708,10 @@ static long btrfs_ioctl_rm_dev_v2(struct }
/* Check for compatibility reject unknown flags */ - if (vol_args->flags & ~BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED) - return -EOPNOTSUPP; + if (vol_args->flags & ~BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED) { + ret = -EOPNOTSUPP; + goto out; + }
if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running, 1)) {