2.6.28-stable review patch. If anyone has any objections, please let us know. ------------------ From: Roland McGrath commit 92dc07b1f988e8c237a38e23be660b9b8533e6fd upstream. The elf_core_dump() code does its work with set_fs(KERNEL_DS) in force, so vma_dump_size() needs to switch back with set_fs(USER_DS) to safely use get_user() for a normal user-space address. Checking for VM_READ optimizes out the case where get_user() would fail anyway. The vm_file check here was already superfluous given the control flow earlier in the function, so that is a cleanup/optimization unrelated to other changes but an obvious and trivial one. Reported-by: Gerald Schaefer Signed-off-by: Roland McGrath Signed-off-by: Greg Kroah-Hartman --- fs/binfmt_elf.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1196,9 +1196,11 @@ static unsigned long vma_dump_size(struc * check for an ELF header. If we find one, dump the first page to * aid in determining what was mapped here. */ - if (FILTER(ELF_HEADERS) && vma->vm_file != NULL && vma->vm_pgoff == 0) { + if (FILTER(ELF_HEADERS) && + vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) { u32 __user *header = (u32 __user *) vma->vm_start; u32 word; + mm_segment_t fs = get_fs(); /* * Doing it this way gets the constant folded by GCC. */ @@ -1211,7 +1213,15 @@ static unsigned long vma_dump_size(struc magic.elfmag[EI_MAG1] = ELFMAG1; magic.elfmag[EI_MAG2] = ELFMAG2; magic.elfmag[EI_MAG3] = ELFMAG3; - if (get_user(word, header) == 0 && word == magic.cmp) + /* + * Switch to the user "segment" for get_user(), + * then put back what elf_core_dump() had in place. + */ + set_fs(USER_DS); + if (unlikely(get_user(word, header))) + word = 0; + set_fs(fs); + if (word == magic.cmp) return PAGE_SIZE; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/