[Crash-utility] Re: [PATCH] netdump: do not close fd prematurely in proc_kcore_init()

When running crash on a live kernel without specifying /proc/kcore as an explicit argument, crash prints an unexpected error message during startup: /proc/kcore: read: Bad file descriptor Commit ad427b7f8ffc ("fix eheader overflow") replaced BCOPY with read(fd, pkd->elf_header, pkd->header_size) to support large ELF headers. However, when kcore_fd == UNUSED, fd was already closed immediately after lseek(fd, 0, SEEK_SET) before read(): if (lseek(fd, 0, SEEK_SET) != 0) { sprintf(buf, "/proc/kcore: lseek"); perror(buf); goto bailout; } if (fd != kcore_fd) close(fd); This causes the subsequent read(fd, pkd->elf_header, pkd->header_size) to fail with EBADF. Move close(fd) to the exit points so that fd remains open until all reads are complete. Also ensure fd is closed via bailout if e_phoff validation fails. Fixes: ad427b7f8ffc ("fix eheader overflow") Signed-off-by: Curu Wong <prinbra(a)gmail.com&gt; --- netdump.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/netdump.c b/netdump.c index 64d4edc..b2cf26d 100644 --- a/netdump.c +++ b/netdump.c @@ -4652,13 +4652,10 @@ proc_kcore_init_32(FILE *fp, int kcore_fd) goto bailout; } - if (fd != kcore_fd) - close(fd); - elf32 = (Elf32_Ehdr *)&eheader[0]; if (elf32->e_phoff > sizeof(eheader) - 2 * sizeof(Elf32_Phdr)) { error(INFO, "/proc/kcore: ELF program header offset too big!\n"); - return FALSE; + goto bailout; } notes32 = (Elf32_Phdr *)&eheader[elf32->e_phoff]; load32 = notes32 + 1; @@ -4691,6 +4688,9 @@ proc_kcore_init_32(FILE *fp, int kcore_fd) kcore_memory_dump(CRASHDEBUG(1) ? fp : pc->nullfp); + if (fd != kcore_fd) + close(fd); + return TRUE; bailout: @@ -4730,13 +4730,10 @@ proc_kcore_init_64(FILE *fp, int kcore_fd) goto bailout; } - if (fd != kcore_fd) - close(fd); - elf64 = (Elf64_Ehdr *)&eheader[0]; if (elf64->e_phoff > sizeof(eheader) - 2 * sizeof(Elf64_Phdr)) { error(INFO, "/proc/kcore: ELF program header offset too big!\n"); - return FALSE; + goto bailout; } notes64 = (Elf64_Phdr *)&eheader[elf64->e_phoff]; load64 = notes64 + 1; @@ -4770,6 +4767,9 @@ proc_kcore_init_64(FILE *fp, int kcore_fd) kcore_memory_dump(CRASHDEBUG(1) ? fp : pc->nullfp); + if (fd != kcore_fd) + close(fd); + return TRUE; bailout: