https://bugzilla.kernel.org/show_bug.cgi?id=200043 Bug ID: 200043 Summary: lseek returns negative and inconsistent positions for directories on ext4 fs Product: File System Version: 2.5 Kernel Version: v4.17 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: ext4 Assignee: fs_ext4@xxxxxxxxxxxxxxxxxxxx Reporter: anatoly.trosinenko@xxxxxxxxx Regression: No When used on a directory FD residing on Ext4 FS, lseek with SEEK_END (and maybe other whence-s) can return negative numbers and leave errno = 0. These numbers in case of SEEK_END are (-1 - offset) and do not accumulate. Reading the lseek(2) man page, I'm not absolutely sure it is a bug, but this seems to be quite strange behavior. How to reproduce: 1. Compile the following code: #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <errno.h> int main(int argc, char *argv[]) { int fd = open(argv[1], O_RDONLY); printf("fd = %d\n", fd); int res = lseek(fd, -10, SEEK_END); printf("lseek returned: %d (errno = %d)\n", res, errno); res = lseek(fd, -1, SEEK_END); printf("lseek returned: %d (errno = %d)\n", res, errno); res = lseek(fd, 0, SEEK_END); printf("lseek returned: %d (errno = %d)\n", res, errno); res = lseek(fd, -11, SEEK_SET); printf("lseek returned: %d (errno = %d)\n", res, errno); return 0; } 2. Run it: # ./lseek_negative /tmp # Suppose the tmpfs is mounted there fd = 3 lseek returned -1 (errno = 22) lseek returned -1 (errno = 22) lseek returned -1 (errno = 22) lseek returned -1 (errno = 22) # ./lseek_negative / # Suppose the / is ext4 fd = 3 lseek returned -11 (errno = 0) lseek returned -2 (errno = 0) lseek returned -1 (errno = 0) <-- Look at the errno value lseek returned -1 (errno = 22) -- You are receiving this mail because: You are watching the assignee of the bug.
