From 06fc40705f23cb7e9af4df2febae8e6889b1a95d Mon Sep 17 00:00:00 2001 From: Rostislav Skudnov Date: Wed, 25 Jul 2018 10:36:38 +0000 Subject: [PATCH] Fix readdir() bug when a non-zero offset is specified in filler 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. This commit is backported from the following commit in 'master' branch: commit 5f125c5e6be24c8d216a4d3c623dc73d742c8c86 Author: Rostislav Date: Sat Jul 21 12:57:09 2018 +0300 Fix readdir() bug when a non-zero offset is specified in filler (#269) --- ChangeLog | 7 ++++++ lib/fuse.c | 10 +++++++-- test/test.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 76 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index 8f6536f..7faf386 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +Unreleased Changes +================== +* 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`. + FUSE 2.9.8 (2018-07-24) ======================= diff --git a/lib/fuse.c b/lib/fuse.c index c3ffb6c..d1d873a 100644 --- a/lib/fuse.c +++ b/lib/fuse.c @@ -3479,10 +3479,14 @@ static int fill_dir(void *dh_, const char *name, const struct stat *statp, } if (off) { + if (dh->filled) { + dh->error = -EIO; + return 1; + } + 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, @@ -3490,6 +3494,8 @@ static int fill_dir(void *dh_, const char *name, const struct stat *statp, if (newlen > dh->needlen) return 1; } else { + dh->filled = 1; + newlen = dh->len + fuse_add_direntry(dh->req, NULL, 0, name, NULL, 0); if (extend_contents(dh, newlen) == -1) @@ -3519,7 +3525,7 @@ 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, fill_dir, off, fi); diff --git a/test/test.c b/test/test.c index 2d3ec72..9dc0eed 100644 --- a/test/test.c +++ b/test/test.c @@ -21,6 +21,7 @@ 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; @@ -80,6 +81,8 @@ 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; @@ -644,6 +647,63 @@ 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; @@ -1641,6 +1701,7 @@ 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); -- 2.30.2