path: root/fs
diff options
authorFilipe Manana <fdmanana@suse.com>2020-01-16 11:29:20 +0000
committerDavid Sterba <dsterba@suse.com>2020-01-17 15:28:52 +0100
commit5afe6ce748c1ea99e0d648153c05075e1ab93afb (patch)
treebccebac0ec57be3d149f6304f2f3952f0bf3d17a /fs
parent6282675e6708ec78518cc0e9ad1f1f73d7c5c53d (diff)
Btrfs: always copy scrub arguments back to user space
If scrub returns an error we are not copying back the scrub arguments structure to user space. This prevents user space to know how much progress scrub has done if an error happened - this includes -ECANCELED which is returned when users ask for scrub to stop. A particular use case, which is used in btrfs-progs, is to resume scrub after it is canceled, in that case it relies on checking the progress from the scrub arguments structure and then use that progress in a call to resume scrub. So fix this by always copying the scrub arguments structure to user space, overwriting the value returned to user space with -EFAULT only if copying the structure failed to let user space know that either that copying did not happen, and therefore the structure is stale, or it happened partially and the structure is probably not valid and corrupt due to the partial copy. Reported-by: Graham Cobb <g.btrfs@cobb.uk.net> Link: https://lore.kernel.org/linux-btrfs/d0a97688-78be-08de-ca7d-bcb4c7fb397e@cobb.uk.net/ Fixes: 06fe39ab15a6a4 ("Btrfs: do not overwrite scrub error with fault error in scrub ioctl") CC: stable@vger.kernel.org # 5.1+ Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Tested-by: Graham Cobb <g.btrfs@cobb.uk.net> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
1 files changed, 13 insertions, 1 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 18e328ce4b54..12ae31e1813e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4252,7 +4252,19 @@ static long btrfs_ioctl_scrub(struct file *file, void __user *arg)
&sa->progress, sa->flags & BTRFS_SCRUB_READONLY,
- if (ret == 0 && copy_to_user(arg, sa, sizeof(*sa)))
+ /*
+ * Copy scrub args to user space even if btrfs_scrub_dev() returned an
+ * error. This is important as it allows user space to know how much
+ * progress scrub has done. For example, if scrub is canceled we get
+ * -ECANCELED from btrfs_scrub_dev() and return that error back to user
+ * space. Later user space can inspect the progress from the structure
+ * btrfs_ioctl_scrub_args and resume scrub from where it left off
+ * previously (btrfs-progs does this).
+ * If we fail to copy the btrfs_ioctl_scrub_args structure to user space
+ * then return -EFAULT to signal the structure was not copied or it may
+ * be corrupt and unreliable due to a partial copy.
+ */
+ if (copy_to_user(arg, sa, sizeof(*sa)))
ret = -EFAULT;
if (!(sa->flags & BTRFS_SCRUB_READONLY))

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