From 30736a4d43f4af7f1a7836d6a266be17082195c4 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Fri, 5 Mar 2010 13:44:12 -0800 Subject: [PATCH] coredump: pass mm->flags as a coredump parameter for consistency Pass mm->flags as a coredump parameter for consistency. --- 1787 if (mm->core_state || !get_dumpable(mm)) { <- (1) 1788 up_write(&mm->mmap_sem); 1789 put_cred(cred); 1790 goto fail; 1791 } 1792 [...] 1798 if (get_dumpable(mm) == 2) { /* Setuid core dump mode */ <-(2) 1799 flag = O_EXCL; /* Stop rewrite attacks */ 1800 cred->fsuid = 0; /* Dump root private */ 1801 } --- Since dumpable bits are not protected by lock, there is a chance to change these bits between (1) and (2). To solve this issue, this patch copies mm->flags to coredump_params.mm_flags at the beginning of do_coredump() and uses it instead of get_dumpable() while dumping core. This copy is also passed to binfmt->core_dump, since elf*_core_dump() uses dump_filter bits in mm->flags. [akpm@linux-foundation.org: fix merge] Signed-off-by: Masami Hiramatsu Acked-by: Roland McGrath Cc: Hidehiro Kawai Cc: Oleg Nesterov Cc: Ingo Molnar Reviewed-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/binfmt_elf.c | 14 +++----------- fs/binfmt_elf_fdpic.c | 14 +++----------- fs/exec.c | 20 ++++++++++++++++---- include/linux/binfmts.h | 1 + 4 files changed, 23 insertions(+), 26 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 78de530cfb02..535e763ab1a6 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1882,7 +1882,6 @@ static int elf_core_dump(struct coredump_params *cprm) struct vm_area_struct *vma, *gate_vma; struct elfhdr *elf = NULL; loff_t offset = 0, dataoff, foffset; - unsigned long mm_flags; struct elf_note_info info; struct elf_phdr *phdr4note = NULL; struct elf_shdr *shdr4extnum = NULL; @@ -1957,14 +1956,7 @@ static int elf_core_dump(struct coredump_params *cprm) dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE); - /* - * We must use the same mm->flags while dumping core to avoid - * inconsistency between the program headers and bodies, otherwise an - * unusable core file can be generated. - */ - mm_flags = current->mm->flags; - - offset += elf_core_vma_data_size(gate_vma, mm_flags); + offset += elf_core_vma_data_size(gate_vma, cprm->mm_flags); offset += elf_core_extra_data_size(); e_shoff = offset; @@ -1995,7 +1987,7 @@ static int elf_core_dump(struct coredump_params *cprm) phdr.p_offset = offset; phdr.p_vaddr = vma->vm_start; phdr.p_paddr = 0; - phdr.p_filesz = vma_dump_size(vma, mm_flags); + phdr.p_filesz = vma_dump_size(vma, cprm->mm_flags); phdr.p_memsz = vma->vm_end - vma->vm_start; offset += phdr.p_filesz; phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0; @@ -2030,7 +2022,7 @@ static int elf_core_dump(struct coredump_params *cprm) unsigned long addr; unsigned long end; - end = vma->vm_start + vma_dump_size(vma, mm_flags); + end = vma->vm_start + vma_dump_size(vma, cprm->mm_flags); for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) { struct page *page; diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index e49d9c06a4b6..6d6a16c5e9bb 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -1626,7 +1626,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm) #endif int thread_status_size = 0; elf_addr_t *auxv; - unsigned long mm_flags; struct elf_phdr *phdr4note = NULL; struct elf_shdr *shdr4extnum = NULL; Elf_Half e_phnum; @@ -1769,14 +1768,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm) /* Page-align dumped data */ dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE); - /* - * We must use the same mm->flags while dumping core to avoid - * inconsistency between the program headers and bodies, otherwise an - * unusable core file can be generated. - */ - mm_flags = current->mm->flags; - - offset += elf_core_vma_data_size(mm_flags); + offset += elf_core_vma_data_size(cprm->mm_flags); offset += elf_core_extra_data_size(); e_shoff = offset; @@ -1809,7 +1801,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm) phdr.p_offset = offset; phdr.p_vaddr = vma->vm_start; phdr.p_paddr = 0; - phdr.p_filesz = maydump(vma, mm_flags) ? sz : 0; + phdr.p_filesz = maydump(vma, cprm->mm_flags) ? sz : 0; phdr.p_memsz = sz; offset += phdr.p_filesz; phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0; @@ -1847,7 +1839,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm) goto end_coredump; if (elf_fdpic_dump_segments(cprm->file, &size, &cprm->limit, - mm_flags) < 0) + cprm->mm_flags) < 0) goto end_coredump; if (!elf_core_write_extra_data(cprm->file, &size, cprm->limit)) diff --git a/fs/exec.c b/fs/exec.c index da2b31dc4e1c..89d4080c1435 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1748,14 +1748,19 @@ void set_dumpable(struct mm_struct *mm, int value) } } -int get_dumpable(struct mm_struct *mm) +static int __get_dumpable(unsigned long mm_flags) { int ret; - ret = mm->flags & 0x3; + ret = mm_flags & MMF_DUMPABLE_MASK; return (ret >= 2) ? 2 : ret; } +int get_dumpable(struct mm_struct *mm) +{ + return __get_dumpable(mm->flags); +} + static void wait_for_dump_helpers(struct file *file) { struct pipe_inode_info *pipe; @@ -1799,6 +1804,12 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs) .signr = signr, .regs = regs, .limit = rlimit(RLIMIT_CORE), + /* + * We must use the same mm->flags while dumping core to avoid + * inconsistency of bit flags, since this flag is not protected + * by any locks. + */ + .mm_flags = mm->flags, }; audit_core_dumps(signr); @@ -1817,7 +1828,7 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs) /* * If another thread got here first, or we are not dumpable, bail out. */ - if (mm->core_state || !get_dumpable(mm)) { + if (mm->core_state || !__get_dumpable(cprm.mm_flags)) { up_write(&mm->mmap_sem); put_cred(cred); goto fail; @@ -1828,7 +1839,8 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs) * process nor do we know its entire history. We only know it * was tainted so we dump it as root in mode 2. */ - if (get_dumpable(mm) == 2) { /* Setuid core dump mode */ + if (__get_dumpable(cprm.mm_flags) == 2) { + /* Setuid core dump mode */ flag = O_EXCL; /* Stop rewrite attacks */ cred->fsuid = 0; /* Dump root private */ } diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 89c6249fc561..c809e286d213 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -74,6 +74,7 @@ struct coredump_params { struct pt_regs *regs; struct file *file; unsigned long limit; + unsigned long mm_flags; }; /* -- 2.20.1