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* [PATCH] btrfs: set tree_root->node = NULL on error
@ 2020-06-30 18:53 Josef Bacik
  2020-07-01  6:23 ` Nikolay Borisov
  2020-07-01 18:05 ` David Sterba
  0 siblings, 2 replies; 3+ messages in thread
From: Josef Bacik @ 2020-06-30 18:53 UTC (permalink / raw)
  To: linux-btrfs, kernel-team; +Cc: Eric Sandeen

Eric reported an issue where mounting -o recovery with a fuzzed fs
resulted in a kernel panic.  This is because we tried to free the tree
node, except it was an error from the read.  Fix this by properly
resetting the tree_root->node == NULL in this case.  The panic was the
following

BTRFS warning (device loop0): failed to read tree root
BUG: kernel NULL pointer dereference, address: 000000000000001f
RIP: 0010:free_extent_buffer+0xe/0x90 [btrfs]
Call Trace:
 free_root_extent_buffers.part.0+0x11/0x30 [btrfs]
 free_root_pointers+0x1a/0xa2 [btrfs]
 open_ctree+0x1776/0x18a5 [btrfs]
 btrfs_mount_root.cold+0x13/0xfa [btrfs]
 ? selinux_fs_context_parse_param+0x37/0x80
 legacy_get_tree+0x27/0x40
 vfs_get_tree+0x25/0xb0
 fc_mount+0xe/0x30
 vfs_kern_mount.part.0+0x71/0x90
 btrfs_mount+0x147/0x3e0 [btrfs]
 ? cred_has_capability+0x7c/0x120
 ? legacy_get_tree+0x27/0x40
 legacy_get_tree+0x27/0x40
 vfs_get_tree+0x25/0xb0
 do_mount+0x735/0xa40
 __x64_sys_mount+0x8e/0xd0
 do_syscall_64+0x4d/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f5302f851be

Fixes: b8522a1e5f42 ("btrfs: Factor out tree roots initialization during mount")
Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/disk-io.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7c07578866f3..c27022f13150 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2592,10 +2592,12 @@ static int __cold init_tree_roots(struct btrfs_fs_info *fs_info)
 		    !extent_buffer_uptodate(tree_root->node)) {
 			handle_error = true;
 
-			if (IS_ERR(tree_root->node))
+			if (IS_ERR(tree_root->node)) {
 				ret = PTR_ERR(tree_root->node);
-			else if (!extent_buffer_uptodate(tree_root->node))
+				tree_root->node = NULL;
+			} else if (!extent_buffer_uptodate(tree_root->node)) {
 				ret = -EUCLEAN;
+			}
 
 			btrfs_warn(fs_info, "failed to read tree root");
 			continue;
-- 
2.24.1


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH] btrfs: set tree_root->node = NULL on error
  2020-06-30 18:53 [PATCH] btrfs: set tree_root->node = NULL on error Josef Bacik
@ 2020-07-01  6:23 ` Nikolay Borisov
  2020-07-01 18:05 ` David Sterba
  1 sibling, 0 replies; 3+ messages in thread
From: Nikolay Borisov @ 2020-07-01  6:23 UTC (permalink / raw)
  To: Josef Bacik, linux-btrfs, kernel-team; +Cc: Eric Sandeen



On 30.06.20 г. 21:53 ч., Josef Bacik wrote:
> Eric reported an issue where mounting -o recovery with a fuzzed fs
> resulted in a kernel panic.  This is because we tried to free the tree
> node, except it was an error from the read.  Fix this by properly
> resetting the tree_root->node == NULL in this case.  The panic was the
> following
> 
> BTRFS warning (device loop0): failed to read tree root
> BUG: kernel NULL pointer dereference, address: 000000000000001f
> RIP: 0010:free_extent_buffer+0xe/0x90 [btrfs]
> Call Trace:
>  free_root_extent_buffers.part.0+0x11/0x30 [btrfs]
>  free_root_pointers+0x1a/0xa2 [btrfs]
>  open_ctree+0x1776/0x18a5 [btrfs]
>  btrfs_mount_root.cold+0x13/0xfa [btrfs]
>  ? selinux_fs_context_parse_param+0x37/0x80
>  legacy_get_tree+0x27/0x40
>  vfs_get_tree+0x25/0xb0
>  fc_mount+0xe/0x30
>  vfs_kern_mount.part.0+0x71/0x90
>  btrfs_mount+0x147/0x3e0 [btrfs]
>  ? cred_has_capability+0x7c/0x120
>  ? legacy_get_tree+0x27/0x40
>  legacy_get_tree+0x27/0x40
>  vfs_get_tree+0x25/0xb0
>  do_mount+0x735/0xa40
>  __x64_sys_mount+0x8e/0xd0
>  do_syscall_64+0x4d/0x90
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7f5302f851be
> 
> Fixes: b8522a1e5f42 ("btrfs: Factor out tree roots initialization during mount")
> Reported-by: Eric Sandeen <sandeen@redhat.com>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/disk-io.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 7c07578866f3..c27022f13150 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -2592,10 +2592,12 @@ static int __cold init_tree_roots(struct btrfs_fs_info *fs_info)
>  		    !extent_buffer_uptodate(tree_root->node)) {
>  			handle_error = true;
>  
> -			if (IS_ERR(tree_root->node))
> +			if (IS_ERR(tree_root->node)) {
>  				ret = PTR_ERR(tree_root->node);
> -			else if (!extent_buffer_uptodate(tree_root->node))
> +				tree_root->node = NULL;
> +			} else if (!extent_buffer_uptodate(tree_root->node)) {
>  				ret = -EUCLEAN;
> +			}

So this is problematic only if we fail on the last iteration of the loop
as this results in init_tree_roots returning err value with
tree_root->node = -ERR. Subsequently the caller does: fail_tree_roots
which calls free_root_pointers on the bogus value. IMO this piece of
information should go into the changelog in some form or another.


>  
>  			btrfs_warn(fs_info, "failed to read tree root");
>  			continue;
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] btrfs: set tree_root->node = NULL on error
  2020-06-30 18:53 [PATCH] btrfs: set tree_root->node = NULL on error Josef Bacik
  2020-07-01  6:23 ` Nikolay Borisov
@ 2020-07-01 18:05 ` David Sterba
  1 sibling, 0 replies; 3+ messages in thread
From: David Sterba @ 2020-07-01 18:05 UTC (permalink / raw)
  To: Josef Bacik; +Cc: linux-btrfs, kernel-team, Eric Sandeen

On Tue, Jun 30, 2020 at 02:53:02PM -0400, Josef Bacik wrote:
> Eric reported an issue where mounting -o recovery with a fuzzed fs
> resulted in a kernel panic.  This is because we tried to free the tree
> node, except it was an error from the read.  Fix this by properly
> resetting the tree_root->node == NULL in this case.  The panic was the
> following
> 
> BTRFS warning (device loop0): failed to read tree root
> BUG: kernel NULL pointer dereference, address: 000000000000001f
> RIP: 0010:free_extent_buffer+0xe/0x90 [btrfs]
> Call Trace:
>  free_root_extent_buffers.part.0+0x11/0x30 [btrfs]
>  free_root_pointers+0x1a/0xa2 [btrfs]
>  open_ctree+0x1776/0x18a5 [btrfs]
>  btrfs_mount_root.cold+0x13/0xfa [btrfs]
>  ? selinux_fs_context_parse_param+0x37/0x80
>  legacy_get_tree+0x27/0x40
>  vfs_get_tree+0x25/0xb0
>  fc_mount+0xe/0x30
>  vfs_kern_mount.part.0+0x71/0x90
>  btrfs_mount+0x147/0x3e0 [btrfs]
>  ? cred_has_capability+0x7c/0x120
>  ? legacy_get_tree+0x27/0x40
>  legacy_get_tree+0x27/0x40
>  vfs_get_tree+0x25/0xb0
>  do_mount+0x735/0xa40
>  __x64_sys_mount+0x8e/0xd0
>  do_syscall_64+0x4d/0x90
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7f5302f851be
> 
> Fixes: b8522a1e5f42 ("btrfs: Factor out tree roots initialization during mount")
> Reported-by: Eric Sandeen <sandeen@redhat.com>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Added to misc-next with Niks explanation, thanks.

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2020-07-01 18:05 UTC | newest]

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2020-06-30 18:53 [PATCH] btrfs: set tree_root->node = NULL on error Josef Bacik
2020-07-01  6:23 ` Nikolay Borisov
2020-07-01 18:05 ` David Sterba

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