Baokun Li (1): ext4: fix slab-use-after-free in ext4_split_extent_at()
Theodore Ts'o (1): ext4: avoid ext4_error()'s caused by ENOMEM in the truncate path
fs/ext4/ext4.h | 1 + fs/ext4/extents.c | 64 +++++++++++++++++++++++++++++++++++++++-------- 2 files changed, 54 insertions(+), 11 deletions(-)
From: Theodore Ts'o tytso@mit.edu
mainline inclusion from mainline-v5.8-rc1 commit 73c384c0cdaa8ea9ca9ef2d0cff6a25930f1648e category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYR9L CVE: CVE-2024-49884
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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We can't fail in the truncate path without requiring an fsck. Add work around for this by using a combination of retry loops and the __GFP_NOFAIL flag.
From: Theodore Ts'o tytso@mit.edu Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Anna Pendleton pendleton@google.com Reviewed-by: Harshad Shirwadkar harshadshirwadkar@gmail.com Link: https://lore.kernel.org/r/20200507175028.15061-1-pendleton@google.com Signed-off-by: Theodore Ts'o tytso@mit.edu
Conflicts: fs/ext4/extents.c [Context differences because there is no commit dd6683e6efad ("ext4: remove ext4_{ind,ext}_calc_metadata_amount()") and commit 9c6e07191379 ("ext4: check for inconsistent extents between index and leaf block").] Signed-off-by: Baokun Li libaokun1@huawei.com --- fs/ext4/ext4.h | 1 + fs/ext4/extents.c | 43 +++++++++++++++++++++++++++++++++---------- 2 files changed, 34 insertions(+), 10 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 1794f5ce1b46..ad174ef1cf85 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -647,6 +647,7 @@ enum { */ #define EXT4_EX_NOCACHE 0x40000000 #define EXT4_EX_FORCE_CACHE 0x20000000 +#define EXT4_EX_NOFAIL 0x10000000
/* * Flags used by ext4_free_blocks diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index e29b55991e8f..0bc64866555f 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -315,11 +315,14 @@ ext4_force_split_extent_at(handle_t *handle, struct inode *inode, { struct ext4_ext_path *path = *ppath; int unwritten = ext4_ext_is_unwritten(path[path->p_depth].p_ext); + int flags = EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_PRE_IO; + + if (nofail) + flags |= EXT4_GET_BLOCKS_METADATA_NOFAIL | EXT4_EX_NOFAIL;
return ext4_split_extent_at(handle, inode, ppath, lblk, unwritten ? EXT4_EXT_MARK_UNWRIT1|EXT4_EXT_MARK_UNWRIT2 : 0, - EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_PRE_IO | - (nofail ? EXT4_GET_BLOCKS_METADATA_NOFAIL:0)); + flags); }
/* @@ -581,9 +584,13 @@ __read_extent_tree_block(const char *function, unsigned int line, struct buffer_head *bh; int err; ext4_fsblk_t pblk; + gfp_t gfp_flags = __GFP_MOVABLE | GFP_NOFS; + + if (flags & EXT4_EX_NOFAIL) + gfp_flags |= __GFP_NOFAIL;
pblk = ext4_idx_pblock(idx); - bh = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS); + bh = sb_getblk_gfp(inode->i_sb, pblk, gfp_flags); if (unlikely(!bh)) return ERR_PTR(-ENOMEM);
@@ -935,6 +942,10 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block, struct ext4_ext_path *path = orig_path ? *orig_path : NULL; short int depth, i, ppos = 0; int ret; + gfp_t gfp_flags = GFP_NOFS; + + if (flags & EXT4_EX_NOFAIL) + gfp_flags |= __GFP_NOFAIL;
eh = ext_inode_hdr(inode); depth = ext_depth(inode); @@ -955,7 +966,7 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block, if (!path) { /* account possible depth increase */ path = kcalloc(depth + 2, sizeof(struct ext4_ext_path), - GFP_NOFS); + gfp_flags); if (unlikely(!path)) return ERR_PTR(-ENOMEM); path[0].p_maxdepth = depth + 1; @@ -1104,9 +1115,13 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, ext4_fsblk_t newblock, oldblock; __le32 border; ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */ + gfp_t gfp_flags = GFP_NOFS; int err = 0; size_t ext_size = 0;
+ if (flags & EXT4_EX_NOFAIL) + gfp_flags |= __GFP_NOFAIL; + /* make decision: where to split? */ /* FIXME: now decision is simplest: at current extent */
@@ -1140,7 +1155,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, * We need this to handle errors and free blocks * upon them. */ - ablocks = kcalloc(depth, sizeof(ext4_fsblk_t), GFP_NOFS); + ablocks = kcalloc(depth, sizeof(ext4_fsblk_t), gfp_flags); if (!ablocks) return -ENOMEM;
@@ -2127,7 +2142,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode, if (next != EXT_MAX_BLOCKS) { ext_debug("next leaf block - %u\n", next); BUG_ON(npath != NULL); - npath = ext4_find_extent(inode, next, NULL, 0); + npath = ext4_find_extent(inode, next, NULL, gb_flags); if (IS_ERR(npath)) return PTR_ERR(npath); BUG_ON(npath->p_depth != path->p_depth); @@ -2944,7 +2959,8 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start, ext4_fsblk_t pblk;
/* find extent for or closest extent to this block */ - path = ext4_find_extent(inode, end, NULL, EXT4_EX_NOCACHE); + path = ext4_find_extent(inode, end, NULL, + EXT4_EX_NOCACHE | EXT4_EX_NOFAIL); if (IS_ERR(path)) { ext4_journal_stop(handle); return PTR_ERR(path); @@ -3026,7 +3042,7 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start, le16_to_cpu(path[k].p_hdr->eh_entries)+1; } else { path = kcalloc(depth + 1, sizeof(struct ext4_ext_path), - GFP_NOFS); + GFP_NOFS | __GFP_NOFAIL); if (path == NULL) { ext4_journal_stop(handle); return -ENOMEM; @@ -3453,7 +3469,7 @@ static int ext4_split_extent(handle_t *handle, * Update path is required because previous ext4_split_extent_at() may * result in split of original leaf or extent zeroout. */ - path = ext4_find_extent(inode, map->m_lblk, ppath, 0); + path = ext4_find_extent(inode, map->m_lblk, ppath, flags); if (IS_ERR(path)) return PTR_ERR(path); depth = ext_depth(inode); @@ -4747,7 +4763,14 @@ int ext4_ext_truncate(handle_t *handle, struct inode *inode) } if (err) return err; - return ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1); +retry_remove_space: + err = ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1); + if (err == -ENOMEM) { + cond_resched(); + congestion_wait(BLK_RW_ASYNC, HZ/50); + goto retry_remove_space; + } + return err; }
static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,
stable inclusion from stable-v5.10.227 commit e52f933598b781d291b9297e39c463536da0e185 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYR9L CVE: CVE-2024-49884
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit c26ab35702f8cd0cdc78f96aa5856bfb77be798f upstream.
We hit the following use-after-free:
================================================================== BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: <TASK> kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...]
Allocated by task 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...]
Freed by task 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ==================================================================
The flow of issue triggering is as follows:
ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // return -ENOMEM or -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. If err is -ENOMEM: ext4_ext_dirty(path + path->p_depth) // path use-after-free !!! b. If err is -EIO and we have EXT_DEBUG defined: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // path also use-after-free !!!
So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path.
In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates.
Fixes: dfe5080939ea ("ext4: drop EXT4_EX_NOFREE_ON_ERR from rest of extents handling code") Cc: stable@kernel.org Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Ojaswin Mujoo ojaswin@linux.ibm.com Tested-by: Ojaswin Mujoo ojaswin@linux.ibm.com Link: https://patch.msgid.link/20240822023545.1994557-4-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Conflicts: fs/ext4/extents.c [Context differences because of hulk patch commit 56531f4ad456 ("[Huawei] ext4:record error information when insert extent failed in 'ext4_split_extent_at'").] Signed-off-by: Baokun Li libaokun1@huawei.com --- fs/ext4/extents.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 0bc64866555f..0ab8fda08f86 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3365,6 +3365,25 @@ static int ext4_split_extent_at(handle_t *handle, goto out; }
+ /* + * Update path is required because previous ext4_ext_insert_extent() + * may have freed or reallocated the path. Using EXT4_EX_NOFAIL + * guarantees that ext4_find_extent() will not return -ENOMEM, + * otherwise -ENOMEM will cause a retry in do_writepages(), and a + * WARN_ON may be triggered in ext4_da_update_reserve_space() due to + * an incorrect ee_len causing the i_reserved_data_blocks exception. + */ + path = ext4_find_extent(inode, ee_block, ppath, + flags | EXT4_EX_NOFAIL); + if (IS_ERR(path)) { + EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld", + split, PTR_ERR(path)); + return PTR_ERR(path); + } + depth = ext_depth(inode); + ex = path[depth].p_ext; + *ppath = path; + if (EXT4_EXT_MAY_ZEROOUT & split_flag) { if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) { if (split_flag & EXT4_EXT_DATA_VALID1) { @@ -3413,7 +3432,7 @@ static int ext4_split_extent_at(handle_t *handle, ext4_ext_dirty(handle, inode, path + path->p_depth); return err; out: - ext4_ext_show_leaf(inode, path); + ext4_ext_show_leaf(inode, *ppath); return err; }
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