6.12-stable review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o tytso@mit.edu
[ Upstream commit 9e28059d56649a7212d5b3f8751ec021154ba3dd ]
This patch addresses an issue where some files in case-insensitive directories become inaccessible due to changes in how the kernel function, utf8_casefold(), generates case-folded strings from the commit 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points").
There are good reasons why this change should be made; it's actually quite stupid that Unicode seems to think that the characters ❤ and ❤️ should be casefolded. Unfortimately because of the backwards compatibility issue, this commit was reverted in 231825b2e1ff.
This problem is addressed by instituting a brute-force linear fallback if a lookup fails on case-folded directory, which does result in a performance hit when looking up files affected by the changing how thekernel treats ignorable Uniode characters, or when attempting to look up non-existent file names. So this fallback can be disabled by setting an encoding flag if in the future, the system administrator or the manufacturer of a mobile handset or tablet can be sure that there was no opportunity for a kernel to insert file names with incompatible encodings.
Fixes: 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points") Signed-off-by: Theodore Ts'o tytso@mit.edu Reviewed-by: Gabriel Krisman Bertazi krisman@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/namei.c | 14 ++++++++++---- include/linux/fs.h | 10 +++++++++- 2 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 286f8fcb74cc9..29c7c0b8295fb 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1462,7 +1462,8 @@ static bool ext4_match(struct inode *parent, * sure cf_name was properly initialized before * considering the calculated hash. */ - if (IS_ENCRYPTED(parent) && fname->cf_name.name && + if (sb_no_casefold_compat_fallback(parent->i_sb) && + IS_ENCRYPTED(parent) && fname->cf_name.name && (fname->hinfo.hash != EXT4_DIRENT_HASH(de) || fname->hinfo.minor_hash != EXT4_DIRENT_MINOR_HASH(de))) return false; @@ -1595,10 +1596,15 @@ static struct buffer_head *__ext4_find_entry(struct inode *dir, * return. Otherwise, fall back to doing a search the * old fashioned way. */ - if (!IS_ERR(ret) || PTR_ERR(ret) != ERR_BAD_DX_DIR) + if (IS_ERR(ret) && PTR_ERR(ret) == ERR_BAD_DX_DIR) + dxtrace(printk(KERN_DEBUG "ext4_find_entry: dx failed, " + "falling back\n")); + else if (!sb_no_casefold_compat_fallback(dir->i_sb) && + *res_dir == NULL && IS_CASEFOLDED(dir)) + dxtrace(printk(KERN_DEBUG "ext4_find_entry: casefold " + "failed, falling back\n")); + else goto cleanup_and_exit; - dxtrace(printk(KERN_DEBUG "ext4_find_entry: dx failed, " - "falling back\n")); ret = NULL; } nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb); diff --git a/include/linux/fs.h b/include/linux/fs.h index a6de8d93838d1..37a01c9d96583 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1197,11 +1197,19 @@ extern int send_sigurg(struct file *file); #define SB_NOUSER BIT(31)
/* These flags relate to encoding and casefolding */ -#define SB_ENC_STRICT_MODE_FL (1 << 0) +#define SB_ENC_STRICT_MODE_FL (1 << 0) +#define SB_ENC_NO_COMPAT_FALLBACK_FL (1 << 1)
#define sb_has_strict_encoding(sb) \ (sb->s_encoding_flags & SB_ENC_STRICT_MODE_FL)
+#if IS_ENABLED(CONFIG_UNICODE) +#define sb_no_casefold_compat_fallback(sb) \ + (sb->s_encoding_flags & SB_ENC_NO_COMPAT_FALLBACK_FL) +#else +#define sb_no_casefold_compat_fallback(sb) (1) +#endif + /* * Umount options */