kernel/linux.git/fs/ext4/dir.c, branch v5.10.257

ext4: fix OOB read when checking dotdot dir

2025-04-10T12:31:02+00:00

commit d5e206778e96e8667d3bde695ad372c296dc9353 upstream. Mounting a corrupted filesystem with directory which contains '.' dir entry with rec_len == block size results in out-of-bounds read (later on, when the corrupted directory is removed). ext4_empty_dir() assumes every ext4 directory contains at least '.' and '..' as directory entries in the first data block. It first loads the '.' dir entry, performs sanity checks by calling ext4_check_dir_entry() and then uses its rec_len member to compute the location of '..' dir entry (in ext4_next_entry). It assumes the '..' dir entry fits into the same data block. If the rec_len of '.' is precisely one block (4KB), it slips through the sanity checks (it is considered the last directory entry in the data block) and leaves "struct ext4_dir_entry_2 *de" point exactly past the memory slot allocated to the data block. The following call to ext4_check_dir_entry() on new value of de then dereferences this pointer which results in out-of-bounds mem access. Fix this by extending __ext4_check_dir_entry() to check for '.' dir entries that reach the end of data block. Make sure to ignore the phony dir entries for checksum (by checking name_len for non-zero). Note: This is reported by KASAN as use-after-free in case another structure was recently freed from the slot past the bound, but it is really an OOB read. This issue was found by syzkaller tool. Call Trace: [ 38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x67e/0x710 [ 38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor/5375 [ 38.595158] [ 38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.0-rc7 #1 [ 38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 38.595304] Call Trace: [ 38.595308] [ 38.595311] dump_stack_lvl+0xa7/0xd0 [ 38.595325] print_address_description.constprop.0+0x2c/0x3f0 [ 38.595339] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595349] print_report+0xaa/0x250 [ 38.595359] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595368] ? kasan_addr_to_slab+0x9/0x90 [ 38.595378] kasan_report+0xab/0xe0 [ 38.595389] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595400] __ext4_check_dir_entry+0x67e/0x710 [ 38.595410] ext4_empty_dir+0x465/0x990 [ 38.595421] ? __pfx_ext4_empty_dir+0x10/0x10 [ 38.595432] ext4_rmdir.part.0+0x29a/0xd10 [ 38.595441] ? __dquot_initialize+0x2a7/0xbf0 [ 38.595455] ? __pfx_ext4_rmdir.part.0+0x10/0x10 [ 38.595464] ? __pfx___dquot_initialize+0x10/0x10 [ 38.595478] ? down_write+0xdb/0x140 [ 38.595487] ? __pfx_down_write+0x10/0x10 [ 38.595497] ext4_rmdir+0xee/0x140 [ 38.595506] vfs_rmdir+0x209/0x670 [ 38.595517] ? lookup_one_qstr_excl+0x3b/0x190 [ 38.595529] do_rmdir+0x363/0x3c0 [ 38.595537] ? __pfx_do_rmdir+0x10/0x10 [ 38.595544] ? strncpy_from_user+0x1ff/0x2e0 [ 38.595561] __x64_sys_unlinkat+0xf0/0x130 [ 38.595570] do_syscall_64+0x5b/0x180 [ 38.595583] entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: ac27a0ec112a0 ("[PATCH] ext4: initial copy of files from ext3") Signed-off-by: Jakub Acs Cc: Theodore Ts'o Cc: Andreas Dilger Cc: linux-ext4@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Mahmoud Adam Cc: stable@vger.kernel.org Cc: security@kernel.org Link: https://patch.msgid.link/b3ae36a6794c4a01944c7d70b403db5b@amazon.de Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

ext4: fix potential infinite loop in ext4_dx_readdir()

2021-10-06T13:56:02+00:00

commit 42cb447410d024e9d54139ae9c21ea132a8c384c upstream. When ext4_htree_fill_tree() fails, ext4_dx_readdir() can run into an infinite loop since if info->last_pos != ctx->pos this will reset the directory scan and reread the failing entry. For example: 1. a dx_dir which has 3 block, block 0 as dx_root block, block 1/2 as leaf block which own the ext4_dir_entry_2 2. block 1 read ok and call_filldir which will fill the dirent and update the ctx->pos 3. block 2 read fail, but we has already fill some dirent, so we will return back to userspace will a positive return val(see ksys_getdents64) 4. the second ext4_dx_readdir will reset the world since info->last_pos != ctx->pos, and will also init the curr_hash which pos to block 1 5. So we will read block1 too, and once block2 still read fail, we can only fill one dirent because the hash of the entry in block1(besides the last one) won't greater than curr_hash 6. this time, we forget update last_pos too since the read for block2 will fail, and since we has got the one entry, ksys_getdents64 can return success 7. Latter we will trapped in a loop with step 4~6 Cc: stable@kernel.org Signed-off-by: yangerkun Reviewed-by: Jan Kara Signed-off-by: Theodore Ts'o Link: https://lore.kernel.org/r/20210914111415.3921954-1-yangerkun@huawei.com Signed-off-by: Greg Kroah-Hartman

ext4: use generic casefolding support

2020-10-28T17:43:13+00:00

This switches ext4 over to the generic support provided in libfs. Since casefolded dentries behave the same in ext4 and f2fs, we decrease the maintenance burden by unifying them, and any optimizations will immediately apply to both. Signed-off-by: Daniel Rosenberg Reviewed-by: Eric Biggers Link: https://lore.kernel.org/r/20201028050820.1636571-1-drosen@google.com Signed-off-by: Theodore Ts'o

Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

2020-10-22T17:31:08+00:00

Pull ext4 updates from Ted Ts'o: "The siginificant new ext4 feature this time around is Harshad's new fast_commit mode. In addition, thanks to Mauricio for fixing a race where mmap'ed pages that are being changed in parallel with a data=journal transaction commit could result in bad checksums in the failure that could cause journal replays to fail. Also notable is Ritesh's buffered write optimization which can result in significant improvements on parallel write workloads. (The kernel test robot reported a 330.6% improvement on fio.write_iops on a 96 core system using DAX) Besides that, we have the usual miscellaneous cleanups and bug fixes" Link: https://lore.kernel.org/r/20200925071217.GO28663@shao2-debian * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (46 commits) ext4: fix invalid inode checksum ext4: add fast commit stats in procfs ext4: add a mount opt to forcefully turn fast commits on ext4: fast commit recovery path jbd2: fast commit recovery path ext4: main fast-commit commit path jbd2: add fast commit machinery ext4 / jbd2: add fast commit initialization ext4: add fast_commit feature and handling for extended mount options doc: update ext4 and journalling docs to include fast commit feature ext4: Detect already used quota file early jbd2: avoid transaction reuse after reformatting ext4: use the normal helper to get the actual inode ext4: fix bs < ps issue reported with dioread_nolock mount opt ext4: data=journal: write-protect pages on j_submit_inode_data_buffers() ext4: data=journal: fixes for ext4_page_mkwrite() jbd2, ext4, ocfs2: introduce/use journal callbacks j_submit|finish_inode_data_buffers() jbd2: introduce/export functions jbd2_journal_submit|finish_inode_data_buffers() ext4: introduce ext4_sb_bread_unmovable() to replace sb_bread_unmovable() ext4: use ext4_sb_bread() instead of sb_bread() ...

ext4: use the normal helper to get the actual inode

2020-10-18T14:37:26+00:00

Here we use the READ_ONCE to fix race conditions in ->d_compare() and ->d_hash() when they are called in RCU-walk mode, seems we can use the normal helper d_inode_rcu() to get the actual inode. Signed-off-by: Kaixu Xia Reviewed-by: Lukas Czerner Link: https://lore.kernel.org/r/1602317416-1260-1-git-send-email-kaixuxia@tencent.com Signed-off-by: Theodore Ts'o

fscrypt: drop unused inode argument from fscrypt_fname_alloc_buffer

2020-09-07T22:27:42+00:00

Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/20200810142139.487631-1-jlayton@kernel.org Signed-off-by: Eric Biggers

ext4: avoid utf8_strncasecmp() with unstable name

2020-06-11T15:01:33+00:00

If the dentry name passed to ->d_compare() fits in dentry::d_iname, then it may be concurrently modified by a rename. This can cause undefined behavior (possibly out-of-bounds memory accesses or crashes) in utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings that may be concurrently modified. Fix this by first copying the filename to a stack buffer if needed. This way we get a stable snapshot of the filename. Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups") Cc: # v5.2+ Cc: Al Viro Cc: Daniel Rosenberg Cc: Gabriel Krisman Bertazi Signed-off-by: Eric Biggers Reviewed-by: Andreas Dilger Link: https://lore.kernel.org/r/20200601200543.59417-1-ebiggers@kernel.org Signed-off-by: Theodore Ts'o

ext4: use flexible-array member in struct fname

2020-03-14T18:43:13+00:00

The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20200309154838.GA31559@embeddedor Signed-off-by: Theodore Ts'o

ext4: fix checksum errors with indexed dirs

2020-02-13T16:56:19+00:00

DIR_INDEX has been introduced as a compat ext4 feature. That means that even kernels / tools that don't understand the feature may modify the filesystem. This works because for kernels not understanding indexed dir format, internal htree nodes appear just as empty directory entries. Index dir aware kernels then check the htree structure is still consistent before using the data. This all worked reasonably well until metadata checksums were introduced. The problem is that these effectively made DIR_INDEX only ro-compatible because internal htree nodes store checksums in a different place than normal directory blocks. Thus any modification ignorant to DIR_INDEX (or just clearing EXT4_INDEX_FL from the inode) will effectively cause checksum mismatch and trigger kernel errors. So we have to be more careful when dealing with indexed directories on filesystems with checksumming enabled. 1) We just disallow loading any directory inodes with EXT4_INDEX_FL when DIR_INDEX is not enabled. This is harsh but it should be very rare (it means someone disabled DIR_INDEX on existing filesystem and didn't run e2fsck), e2fsck can fix the problem, and we don't want to answer the difficult question: "Should we rather corrupt the directory more or should we ignore that DIR_INDEX feature is not set?" 2) When we find out htree structure is corrupted (but the filesystem and the directory should in support htrees), we continue just ignoring htree information for reading but we refuse to add new entries to the directory to avoid corrupting it more. Link: https://lore.kernel.org/r/20200210144316.22081-1-jack@suse.cz Fixes: dbe89444042a ("ext4: Calculate and verify checksums for htree nodes") Reviewed-by: Andreas Dilger Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o Cc: stable@kernel.org

Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

2020-01-30T23:17:05+00:00

Pull ext4 updates from Ted Ts'o: "This merge window, we've added some performance improvements in how we handle inode locking in the read/write paths, and improving the performance of Direct I/O overwrites. We also now record the error code which caused the first and most recent ext4_error() report in the superblock, to make it easier to root cause problems in production systems. There are also many of the usual cleanups and miscellaneous bug fixes" * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (49 commits) jbd2: clean __jbd2_journal_abort_hard() and __journal_abort_soft() jbd2: make sure ESHUTDOWN to be recorded in the journal superblock ext4, jbd2: ensure panic when aborting with zero errno jbd2: switch to use jbd2_journal_abort() when failed to submit the commit record jbd2_seq_info_next should increase position index jbd2: remove pointless assertion in __journal_remove_journal_head ext4,jbd2: fix comment and code style jbd2: delete the duplicated words in the comments ext4: fix extent_status trace points ext4: fix symbolic enum printing in trace output ext4: choose hardlimit when softlimit is larger than hardlimit in ext4_statfs_project() ext4: fix race conditions in ->d_compare() and ->d_hash() ext4: make dioread_nolock the default ext4: fix extent_status fragmentation for plain files jbd2: clear JBD2_ABORT flag before journal_reset to update log tail info when load journal ext4: drop ext4_kvmalloc() ext4: Add EXT4_IOC_FSGETXATTR/EXT4_IOC_FSSETXATTR to compat_ioctl ext4: remove unused macro MPAGE_DA_EXTENT_TAIL ext4: add missing braces in ext4_ext_drop_refs() ext4: fix some nonstandard indentation in extents.c ...