From 8c888b31903cc2acfbf054c23d702caf68857810 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 19 Nov 2025 19:45:04 -0500 Subject: struct filename: saner handling of long names Always allocate struct filename from names_cachep, long name or short; short names would be embedded into struct filename. Longer ones do not cannibalize the original struct filename - put them into kmalloc'ed buffers (PATH_MAX-sized for import from userland, strlen() + 1 - for ones originating kernel-side, where we know the length beforehand). Cutoff length for short names is chosen so that struct filename would be 192 bytes long - that's both a multiple of 64 and large enough to cover the majority of real-world uses. Simplifies logics in getname()/putname() and friends. [fixed an embarrassing braino in EMBEDDED_NAME_MAX, first reported by Dan Carpenter] Signed-off-by: Al Viro --- include/linux/fs.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 997d515bab32..f0f1e8034539 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2409,13 +2409,19 @@ extern struct kobject *fs_kobj; /* fs/open.c */ struct audit_names; -struct filename { + +struct __filename_head { const char *name; /* pointer to actual string */ atomic_t refcnt; struct audit_names *aname; - const char iname[]; +}; +#define EMBEDDED_NAME_MAX (192 - sizeof(struct __filename_head)) +struct filename { + struct __filename_head; + const char iname[EMBEDDED_NAME_MAX]; }; static_assert(offsetof(struct filename, iname) % sizeof(long) == 0); +static_assert(sizeof(struct filename) % 64 == 0); static inline struct mnt_idmap *file_mnt_idmap(const struct file *file) { -- cgit v1.2.3