The fix of CVE-2024-37354 1ff2bd566fbc doesn't apply cleanly to 5.15 as it requires an extra prequisite patch `8a2b3da191e5a btrfs: add helper to truncate inode items when logging inode` for the context to be the same. Therefore two patches were brought back as part of this backport.
The prerequisite patch is part of a 10 patch patch series however bringing all of them back felt more of a feature backport rather than CVE fix. Please let me know if bringing the entire series back is more preferrable then I shall re-send v2.
Some basic smoke testing and btrfs testing on inhouse test suite was done and no regressions were observerd.
Filipe Manana (1): btrfs: add helper to truncate inode items when logging inode
Omar Sandoval (1): btrfs: fix crash on racing fsync and size-extending write into prealloc
fs/btrfs/tree-log.c | 47 ++++++++++++++++++++++++++++----------------- 1 file changed, 29 insertions(+), 18 deletions(-)
From: Omar Sandoval osandov@fb.com
commit 9d274c19a71b3a276949933859610721a453946b upstream.
We have been seeing crashes on duplicate keys in btrfs_set_item_key_safe():
BTRFS critical (device vdb): slot 4 key (450 108 8192) new key (450 108 8192) ------------[ cut here ]------------ kernel BUG at fs/btrfs/ctree.c:2620! invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 3139 Comm: xfs_io Kdump: loaded Not tainted 6.9.0 #6 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/2014 RIP: 0010:btrfs_set_item_key_safe+0x11f/0x290 [btrfs]
With the following stack trace:
#0 btrfs_set_item_key_safe (fs/btrfs/ctree.c:2620:4) #1 btrfs_drop_extents (fs/btrfs/file.c:411:4) #2 log_one_extent (fs/btrfs/tree-log.c:4732:9) #3 btrfs_log_changed_extents (fs/btrfs/tree-log.c:4955:9) #4 btrfs_log_inode (fs/btrfs/tree-log.c:6626:9) #5 btrfs_log_inode_parent (fs/btrfs/tree-log.c:7070:8) #6 btrfs_log_dentry_safe (fs/btrfs/tree-log.c:7171:8) #7 btrfs_sync_file (fs/btrfs/file.c:1933:8) #8 vfs_fsync_range (fs/sync.c:188:9) #9 vfs_fsync (fs/sync.c:202:9) #10 do_fsync (fs/sync.c:212:9) #11 __do_sys_fdatasync (fs/sync.c:225:9) #12 __se_sys_fdatasync (fs/sync.c:223:1) #13 __x64_sys_fdatasync (fs/sync.c:223:1) #14 do_syscall_x64 (arch/x86/entry/common.c:52:14) #15 do_syscall_64 (arch/x86/entry/common.c:83:7) #16 entry_SYSCALL_64+0xaf/0x14c (arch/x86/entry/entry_64.S:121)
So we're logging a changed extent from fsync, which is splitting an extent in the log tree. But this split part already exists in the tree, triggering the BUG().
This is the state of the log tree at the time of the crash, dumped with drgn (https://github.com/osandov/drgn/blob/main/contrib/btrfs_tree.py) to get more details than btrfs_print_leaf() gives us:
print_extent_buffer(prog.crashed_thread().stack_trace()[0]["eb"])
leaf 33439744 level 0 items 72 generation 9 owner 18446744073709551610 leaf 33439744 flags 0x100000000000000 fs uuid e5bd3946-400c-4223-8923-190ef1f18677 chunk uuid d58cb17e-6d02-494a-829a-18b7d8a399da item 0 key (450 INODE_ITEM 0) itemoff 16123 itemsize 160 generation 7 transid 9 size 8192 nbytes 8473563889606862198 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 204 flags 0x10(PREALLOC) atime 1716417703.220000000 (2024-05-22 15:41:43) ctime 1716417704.983333333 (2024-05-22 15:41:44) mtime 1716417704.983333333 (2024-05-22 15:41:44) otime 17592186044416.000000000 (559444-03-08 01:40:16) item 1 key (450 INODE_REF 256) itemoff 16110 itemsize 13 index 195 namelen 3 name: 193 item 2 key (450 XATTR_ITEM 1640047104) itemoff 16073 itemsize 37 location key (0 UNKNOWN.0 0) type XATTR transid 7 data_len 1 name_len 6 name: user.a data a item 3 key (450 EXTENT_DATA 0) itemoff 16020 itemsize 53 generation 9 type 1 (regular) extent data disk byte 303144960 nr 12288 extent data offset 0 nr 4096 ram 12288 extent compression 0 (none) item 4 key (450 EXTENT_DATA 4096) itemoff 15967 itemsize 53 generation 9 type 2 (prealloc) prealloc data disk byte 303144960 nr 12288 prealloc data offset 4096 nr 8192 item 5 key (450 EXTENT_DATA 8192) itemoff 15914 itemsize 53 generation 9 type 2 (prealloc) prealloc data disk byte 303144960 nr 12288 prealloc data offset 8192 nr 4096 ...
So the real problem happened earlier: notice that items 4 (4k-12k) and 5 (8k-12k) overlap. Both are prealloc extents. Item 4 straddles i_size and item 5 starts at i_size.
Here is the state of the filesystem tree at the time of the crash:
root = prog.crashed_thread().stack_trace()[2]["inode"].root ret, nodes, slots = btrfs_search_slot(root, BtrfsKey(450, 0, 0)) print_extent_buffer(nodes[0])
leaf 30425088 level 0 items 184 generation 9 owner 5 leaf 30425088 flags 0x100000000000000 fs uuid e5bd3946-400c-4223-8923-190ef1f18677 chunk uuid d58cb17e-6d02-494a-829a-18b7d8a399da ... item 179 key (450 INODE_ITEM 0) itemoff 4907 itemsize 160 generation 7 transid 7 size 4096 nbytes 12288 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 6 flags 0x10(PREALLOC) atime 1716417703.220000000 (2024-05-22 15:41:43) ctime 1716417703.220000000 (2024-05-22 15:41:43) mtime 1716417703.220000000 (2024-05-22 15:41:43) otime 1716417703.220000000 (2024-05-22 15:41:43) item 180 key (450 INODE_REF 256) itemoff 4894 itemsize 13 index 195 namelen 3 name: 193 item 181 key (450 XATTR_ITEM 1640047104) itemoff 4857 itemsize 37 location key (0 UNKNOWN.0 0) type XATTR transid 7 data_len 1 name_len 6 name: user.a data a item 182 key (450 EXTENT_DATA 0) itemoff 4804 itemsize 53 generation 9 type 1 (regular) extent data disk byte 303144960 nr 12288 extent data offset 0 nr 8192 ram 12288 extent compression 0 (none) item 183 key (450 EXTENT_DATA 8192) itemoff 4751 itemsize 53 generation 9 type 2 (prealloc) prealloc data disk byte 303144960 nr 12288 prealloc data offset 8192 nr 4096
Item 5 in the log tree corresponds to item 183 in the filesystem tree, but nothing matches item 4. Furthermore, item 183 is the last item in the leaf.
btrfs_log_prealloc_extents() is responsible for logging prealloc extents beyond i_size. It first truncates any previously logged prealloc extents that start beyond i_size. Then, it walks the filesystem tree and copies the prealloc extent items to the log tree.
If it hits the end of a leaf, then it calls btrfs_next_leaf(), which unlocks the tree and does another search. However, while the filesystem tree is unlocked, an ordered extent completion may modify the tree. In particular, it may insert an extent item that overlaps with an extent item that was already copied to the log tree.
This may manifest in several ways depending on the exact scenario, including an EEXIST error that is silently translated to a full sync, overlapping items in the log tree, or this crash. This particular crash is triggered by the following sequence of events:
- Initially, the file has i_size=4k, a regular extent from 0-4k, and a prealloc extent beyond i_size from 4k-12k. The prealloc extent item is the last item in its B-tree leaf. - The file is fsync'd, which copies its inode item and both extent items to the log tree. - An xattr is set on the file, which sets the BTRFS_INODE_COPY_EVERYTHING flag. - The range 4k-8k in the file is written using direct I/O. i_size is extended to 8k, but the ordered extent is still in flight. - The file is fsync'd. Since BTRFS_INODE_COPY_EVERYTHING is set, this calls copy_inode_items_to_log(), which calls btrfs_log_prealloc_extents(). - btrfs_log_prealloc_extents() finds the 4k-12k prealloc extent in the filesystem tree. Since it starts before i_size, it skips it. Since it is the last item in its B-tree leaf, it calls btrfs_next_leaf(). - btrfs_next_leaf() unlocks the path. - The ordered extent completion runs, which converts the 4k-8k part of the prealloc extent to written and inserts the remaining prealloc part from 8k-12k. - btrfs_next_leaf() does a search and finds the new prealloc extent 8k-12k. - btrfs_log_prealloc_extents() copies the 8k-12k prealloc extent into the log tree. Note that it overlaps with the 4k-12k prealloc extent that was copied to the log tree by the first fsync. - fsync calls btrfs_log_changed_extents(), which tries to log the 4k-8k extent that was written. - This tries to drop the range 4k-8k in the log tree, which requires adjusting the start of the 4k-12k prealloc extent in the log tree to 8k. - btrfs_set_item_key_safe() sees that there is already an extent starting at 8k in the log tree and calls BUG().
Fix this by detecting when we're about to insert an overlapping file extent item in the log tree and truncating the part that would overlap.
CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Omar Sandoval osandov@fb.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org (cherry picked from commit 1ff2bd566fbcefcb892be85c493bdb92b911c428) Signed-off-by: Harshvardhan Jha harshvardhan.j.jha@oracle.com --- fs/btrfs/tree-log.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 81826aa1a3f1d..0c8203cca2088 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -4558,18 +4558,23 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans, path->slots[0]++; continue; } - if (!dropped_extents) { - /* - * Avoid logging extent items logged in past fsync calls - * and leading to duplicate keys in the log tree. - */ + /* + * Avoid overlapping items in the log tree. The first time we + * get here, get rid of everything from a past fsync. After + * that, if the current extent starts before the end of the last + * extent we copied, truncate the last one. This can happen if + * an ordered extent completion modifies the subvolume tree + * while btrfs_next_leaf() has the tree unlocked. + */ + if (!dropped_extents || key.offset < truncate_offset) { ret = truncate_inode_items(trans, root->log_root, inode, - truncate_offset, + min(key.offset, truncate_offset), BTRFS_EXTENT_DATA_KEY); if (ret) goto out; dropped_extents = true; } + truncate_offset = btrfs_file_extent_end(path); if (ins_nr == 0) start_slot = slot; ins_nr++;
From: Filipe Manana fdmanana@suse.com
Move the call to btrfs_truncate_inode_items(), and the surrounding retry loop, into a local helper function. This avoids some repetition and avoids making the next change a bit awkward due to a bit of too much indentation.
This patch is part of a patch set comprised of the following patches:
btrfs: check if a log tree exists at inode_logged() btrfs: remove no longer needed checks for NULL log context btrfs: do not log new dentries when logging that a new name exists btrfs: always update the logged transaction when logging new names btrfs: avoid expensive search when dropping inode items from log btrfs: add helper to truncate inode items when logging inode btrfs: avoid expensive search when truncating inode items from the log btrfs: avoid search for logged i_size when logging inode if possible btrfs: avoid attempt to drop extents when logging inode for the first time btrfs: do not commit delayed inode when logging a file in full sync mode
This is patch 6/10 and test results are listed in the change log of the last patch in the set.
Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com (cherry picked from commit 8a2b3da191e5a167bba9776e109b775b21cb4d85) Signed-off-by: Harshvardhan Jha harshvardhan.j.jha@oracle.com --- fs/btrfs/tree-log.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 34fedac4e1864..81826aa1a3f1d 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -3955,6 +3955,21 @@ static int drop_objectid_items(struct btrfs_trans_handle *trans, return ret; }
+static int truncate_inode_items(struct btrfs_trans_handle *trans, + struct btrfs_root *log_root, + struct btrfs_inode *inode, + u64 new_size, u32 min_type) +{ + int ret; + + do { + ret = btrfs_truncate_inode_items(trans, log_root, inode, + new_size, min_type, NULL); + } while (ret == -EAGAIN); + + return ret; +} + static void fill_inode_item(struct btrfs_trans_handle *trans, struct extent_buffer *leaf, struct btrfs_inode_item *item, @@ -4548,13 +4563,9 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans, * Avoid logging extent items logged in past fsync calls * and leading to duplicate keys in the log tree. */ - do { - ret = btrfs_truncate_inode_items(trans, - root->log_root, - inode, truncate_offset, - BTRFS_EXTENT_DATA_KEY, - NULL); - } while (ret == -EAGAIN); + ret = truncate_inode_items(trans, root->log_root, inode, + truncate_offset, + BTRFS_EXTENT_DATA_KEY); if (ret) goto out; dropped_extents = true; @@ -5531,12 +5542,7 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans, &inode->runtime_flags); clear_bit(BTRFS_INODE_COPY_EVERYTHING, &inode->runtime_flags); - while(1) { - ret = btrfs_truncate_inode_items(trans, - log, inode, 0, 0, NULL); - if (ret != -EAGAIN) - break; - } + ret = truncate_inode_items(trans, log, inode, 0, 0); } } else if (test_and_clear_bit(BTRFS_INODE_COPY_EVERYTHING, &inode->runtime_flags) ||
linux-stable-mirror@lists.linaro.org
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Harshvardhan Jha