From 5f125c5e6be24c8d216a4d3c623dc73d742c8c86 Mon Sep 17 00:00:00 2001 From: Rostislav Date: Sat, 21 Jul 2018 12:57:09 +0300 Subject: Fix readdir() bug when a non-zero offset is specified in filler (#269) 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. --- ChangeLog.rst | 8 +++++++ lib/fuse.c | 26 ++++++++++++---------- test/test_syscalls.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 84 insertions(+), 11 deletions(-) diff --git a/ChangeLog.rst b/ChangeLog.rst index cf5450e..9ba0263 100644 --- a/ChangeLog.rst +++ b/ChangeLog.rst @@ -1,3 +1,11 @@ +libfuse 3.2.5 +========================== + +* Added a test of `seekdir` to test_syscalls. +* Fixed `readdir` bug when non-zero offsets are given to filler and the + filesystem client, after reading a whole directory, re-reads it from a + non-zero offset e. g. by calling `seekdir` followed by `readdir`. + libfuse 3.2.4 (2018-07-11) ========================== diff --git a/lib/fuse.c b/lib/fuse.c index 334b977..ea7d3b3 100644 --- a/lib/fuse.c +++ b/lib/fuse.c @@ -3455,6 +3455,11 @@ static int fill_dir(void *dh_, const char *name, const struct stat *statp, if (off) { size_t newlen; + if (dh->filled) { + dh->error = -EIO; + return 1; + } + if (dh->first) { dh->error = -EIO; return 1; @@ -3463,7 +3468,6 @@ static int fill_dir(void *dh_, const char *name, const struct stat *statp, if (extend_contents(dh, dh->needlen) == -1) return 1; - dh->filled = 0; newlen = dh->len + fuse_add_direntry(dh->req, dh->contents + dh->len, dh->needlen - dh->len, name, @@ -3473,10 +3477,8 @@ static int fill_dir(void *dh_, const char *name, const struct stat *statp, dh->len = newlen; } else { - if (!dh->filled) { - dh->error = -EIO; - return 1; - } + dh->filled = 1; + if (fuse_add_direntry_to_dh(dh, name, &stbuf) == -1) return 1; } @@ -3526,6 +3528,11 @@ static int fill_dir_plus(void *dh_, const char *name, const struct stat *statp, if (off) { size_t newlen; + if (dh->filled) { + dh->error = -EIO; + return 1; + } + if (dh->first) { dh->error = -EIO; return 1; @@ -3533,7 +3540,6 @@ static int fill_dir_plus(void *dh_, const char *name, const struct stat *statp, if (extend_contents(dh, dh->needlen) == -1) return 1; - dh->filled = 0; newlen = dh->len + fuse_add_direntry_plus(dh->req, dh->contents + dh->len, dh->needlen - dh->len, name, @@ -3542,10 +3548,8 @@ static int fill_dir_plus(void *dh_, const char *name, const struct stat *statp, return 1; dh->len = newlen; } else { - if (!dh->filled) { - dh->error = -EIO; - return 1; - } + dh->filled = 1; + if (fuse_add_direntry_to_dh(dh, name, &e.attr) == -1) return 1; } @@ -3588,7 +3592,7 @@ static int readdir_fill(struct fuse *f, fuse_req_t req, fuse_ino_t ino, dh->len = 0; dh->error = 0; dh->needlen = size; - dh->filled = 1; + dh->filled = 0; dh->req = req; fuse_prepare_interrupt(f, req, &d); err = fuse_fs_readdir(f->fs, path, dh, filler, off, fi, flags); diff --git a/test/test_syscalls.c b/test/test_syscalls.c index 38a37a1..4e1dc07 100644 --- a/test/test_syscalls.c +++ b/test/test_syscalls.c @@ -28,6 +28,7 @@ static char testname[256]; static char testdata[] = "abcdefghijklmnopqrstuvwxyz"; static char testdata2[] = "1234567890-=qwertyuiop[]\asdfghjkl;'zxcvbnm,./"; static const char *testdir_files[] = { "f1", "f2", NULL}; +static long seekdir_offsets[4]; static char zerodata[4096]; static int testdatalen = sizeof(testdata) - 1; static int testdata2len = sizeof(testdata2) - 1; @@ -87,6 +88,8 @@ static void __start_test(const char *fmt, ...) #define PERROR(msg) test_perror(__FUNCTION__, msg) #define ERROR(msg, args...) test_error(__FUNCTION__, msg, ##args) +#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) + static int check_size(const char *path, int len) { struct stat stbuf; @@ -651,6 +654,63 @@ static int test_ftruncate(int len, int mode) return 0; } +static int test_seekdir(void) +{ + int i; + int res; + DIR *dp; + struct dirent *de; + + start_test("seekdir"); + res = create_dir(testdir, testdir_files); + if (res == -1) + return res; + + dp = opendir(testdir); + if (dp == NULL) { + PERROR("opendir"); + return -1; + } + + /* Remember dir offsets */ + for (i = 0; i < ARRAY_SIZE(seekdir_offsets); i++) { + seekdir_offsets[i] = telldir(dp); + errno = 0; + de = readdir(dp); + if (de == NULL) { + if (errno) { + PERROR("readdir"); + goto fail; + } + break; + } + } + + /* Walk until the end of directory */ + while (de) + de = readdir(dp); + + /* Start from the last valid dir offset and seek backwards */ + for (i--; i >= 0; i--) { + seekdir(dp, seekdir_offsets[i]); + de = readdir(dp); + if (de == NULL) { + ERROR("Unexpected end of directory after seekdir()"); + goto fail; + } + } + + closedir(dp); + res = cleanup_dir(testdir, testdir_files, 0); + if (!res) + success(); + return res; +fail: + closedir(dp); + cleanup_dir(testdir, testdir_files, 1); + return -1; +} + static int test_utime(void) { struct utimbuf utm; @@ -1677,6 +1737,7 @@ int main(int argc, char *argv[]) err += test_rename_file(); err += test_rename_dir(); err += test_rename_dir_loop(); + err += test_seekdir(); err += test_utime(); err += test_truncate(0); err += test_truncate(testdatalen / 2); -- cgit v1.2.3