FYI, this warning was introduced by 0723a0473fb4 ("btrfs: allow
mounting btrfs subvolumes with different ro/rw options").
It looks like "newargs" is eventually used in mount_fs(), so I think
this one is real.
---------- Forwarded message ----------
From: <scan-admin@xxxxxxxxxxxx>
Date: Sat, Apr 12, 2014 at 1:24 AM
Subject: New Defects reported by Coverity Scan for Linux
...
** CID 1201425: Use after free (USE_AFTER_FREE)
/fs/btrfs/super.c: 1193 in mount_subvol()
/fs/btrfs/super.c: 1197 in mount_subvol()
...
________________________________________________________________________________________________________
*** CID 1201425: Use after free (USE_AFTER_FREE)
/fs/btrfs/super.c: 1193 in mount_subvol()
1187 mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
1188 newargs);
1189 kfree(newargs);
1190
1191 if (PTR_RET(mnt) == -EBUSY) {
1192 if (flags & MS_RDONLY) {
>>> CID 1201425: Use after free (USE_AFTER_FREE)
>>> Passing freed pointer "newargs" as an argument to "vfs_kern_mount".
1193 mnt = vfs_kern_mount(&btrfs_fs_type,
flags & ~MS_RDONLY, device_name,
1194 newargs);
1195 } else {
1196 int r;
1197 mnt = vfs_kern_mount(&btrfs_fs_type,
flags | MS_RDONLY, device_name,
1198 newargs);
/fs/btrfs/super.c: 1197 in mount_subvol()
1191 if (PTR_RET(mnt) == -EBUSY) {
1192 if (flags & MS_RDONLY) {
1193 mnt = vfs_kern_mount(&btrfs_fs_type,
flags & ~MS_RDONLY, device_name,
1194 newargs);
1195 } else {
1196 int r;
>>> CID 1201425: Use after free (USE_AFTER_FREE)
>>> Passing freed pointer "newargs" as an argument to "vfs_kern_mount".
1197 mnt = vfs_kern_mount(&btrfs_fs_type,
flags | MS_RDONLY, device_name,
1198 newargs);
1199 if (IS_ERR(mnt))
1200 return ERR_CAST(mnt);
1201
1202 r = btrfs_remount(mnt->mnt_sb, &flags, NULL);
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