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sprintf(3)/snprintf(3) destination buffers need to be large enough
so that gcc doesn't warn -Wformat-truncation= or -Wformat-overflow=
when source buffer size is 1024 bytes.
--
../test/test_syscalls.c:1445:47: warning: '%s' directive output may be truncated writing 1 byte into a region of size between 0 and 1023 [-Wformat-truncation=]
#define PATH(p) (snprintf(path, sizeof path, "%s/%s", testdir, p), path)
^~~~~~~
../test/test_syscalls.c:1458:19:
res = mkdir(PATH("a"), 0755);
~~~
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>
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The bug occurs when a filesystem client reads a directory until the end,
seeks using seekdir() to some valid non-zero position and calls
readdir(). A valid 'struct dirent *' is expected, but NULL is returned
instead. Pseudocode demonstrating the bug:
DIR *dp = opendir("some_dir");
struct dirent *de = readdir(dp);
/* Get offset of the second entry */
long offset = telldir(dp);
/* Read directory until the end */
while (de)
de = readdir(de);
seekdir(dp, offset);
de = readdir(dp);
/* de must contain the second entry, but NULL is returned instead */
The reason of the bug is that when the end of directory is reached, the
kernel calls FUSE_READDIR op with an offset at the end of directory, so
the filesystem's .readdir callback never calls the filler function, and
we end up with dh->filled set to 1. After seekdir(), FUSE_READDIR is
called again with a new offset, but this time the filesystem's .readdir
callback is never called, and an empty reply is returned.
Fix by setting dh->filled to 1 only when zero offsets are given to
filler function.
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Linux performs the dir loop check (rename(a, a/b/c)
or rename(a/b/c, a), etc.) in kernel. Unfortunately
other systems do not perform this check (e.g. FreeBSD).
This results in a deadlock in get_path2, because libfuse
did not expect to handle such cases.
We add a check_dir_loop function that performs the dir
loop check in user mode and enable it on systems that
need it.
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Some filesystems don't track this for directories.
Fixes: #180.
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