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175688 |
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26-Jan-2008 |
yar |
Our fts(3) API, as inherited from 4.4BSD, suffers from integer
fields in FTS and FTSENT structs being too narrow. In addition,
the narrow types creep from there into fts.c. As a result, fts(3)
consumers, e.g., find(1) or rm(1), can't handle file trees an ordinary
user can create, which can have security implications.
To fix the historic implementation of fts(3), OpenBSD and NetBSD
have already changed <fts.h> in somewhat incompatible ways, so we
are free to do so, too. This change is a superset of changes from
the other BSDs with a few more improvements. It doesn't touch
fts(3) functionality; it just extends integer types used by it to
match modern reality and the C standard.
Here are its points:
o For C object sizes, use size_t unless it's 100% certain that
the object will be really small. (Note that fts(3) can construct
pathnames _much_ longer than PATH_MAX for its consumers.)
o Avoid the short types because on modern platforms using them
results in larger and slower code. Change shorts to ints as
follows:
- For variables than count simple, limited things like states,
use plain vanilla `int' as it's the type of choice in C.
- For a limited number of bit flags use `unsigned' because signed
bit-wise operations are implementation-defined, i.e., unportable,
in C.
o For things that should be at least 64 bits wide, use long long
and not int64_t, as the latter is an optional type. See
FTSENT.fts_number aka FTS.fts_bignum. Extending fts_number `to
satisfy future needs' is pointless because there is fts_pointer,
which can be used to link to arbitrary data from an FTSENT.
However, there already are fts(3) consumers that require fts_number,
or fts_bignum, have at least 64 bits in it, so we must allow for them.
o For the tree depth, use `long'. This is a trade-off between making
this field too wide and allowing for 64-bit inode numbers and/or
chain-mounted filesystems. On the one hand, `long' is almost
enough for 32-bit filesystems on a 32-bit platform (our ino_t is
uint32_t now). On the other hand, platforms with a 64-bit (or
wider) `long' will be ready for 64-bit inode numbers, as well as
for several 32-bit filesystems mounted one under another. Note
that fts_level has to be signed because -1 is a magic value for it,
FTS_ROOTPARENTLEVEL.
o For the `nlinks' local var in fts_build(), use `long'. The logic
in fts_build() requires that `nlinks' be signed, but our nlink_t
currently is uint16_t. Therefore let's make the signed var wide
enough to be able to represent 2^16-1 in pure C99, and even 2^32-1
on a 64-bit platform. Perhaps the logic should be changed just
to use nlink_t, but it can be done later w/o breaking fts(3) ABI
any more because `nlinks' is just a local var.
This commit also inludes supporting stuff for the fts change:
o Preserve the old versions of fts(3) functions through libc symbol
versioning because the old versions appeared in all our former releases.
o Bump __FreeBSD_version just in case. There is a small chance that
some ill-written 3-rd party apps may fail to build or work correctly
if compiled after this change.
o Update the fts(3) manpage accordingly. In particular, remove
references to fts_bignum, which was a FreeBSD-specific hack to work
around the too narrow types of FTSENT members. Now fts_number is
at least 64 bits wide (long long) and fts_bignum is an undocumented
alias for fts_number kept around for compatibility reasons. According
to Google Code Search, the only big consumers of fts_bignum are in
our own source tree, so they can be fixed easily to use fts_number.
o Mention the change in src/UPDATING.
PR: bin/104458
Approved by: re (quite a while ago)
Discussed with: deischen (the symbol versioning part)
Reviewed by: -arch (mostly silence); das (generally OK, but we didn't
agree on some types used; assuming that no objections on
-arch let me to stick to my opinion)
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| #
103726 |
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20-Sep-2002 |
wollman |
Make the threatened fts(3) ABI fix. FTSENT now avoids the use of the struct
hack, thereby allowing future extensions to the structure (e.g., for extended
attributes) without rebreaking the ABI. FTSENT now contains a pointer to the
parent stream, which fts_compar() can then take advantage of, avoiding the
undefined behavior previously warned about. As a consequence of this change,
the prototype of the comparison function passed to fts_open() has changed
to reflect the required amount of constness for its use. All callers in the
tree are updated to use the correct prototype.
Comparison functions can now make use of the new parent pointer to access
the new stream-specific private data pointer, which is intended to assist
creation of reentrant library routines which use fts(3) internally.
Not objected to in spirit by: -arch
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