/proc/<pid>/status can report extremely high VmLib values which will confuse monitoring tools. VmLib is mm->exec_vm minus text size, where exec_vm is the number of bytes backed by an executable memory mapping and text size is mm->end_code - mm->start_code as set up by binfmt.
For the vast majority of all programs text size is smaller than exec_vm. But if a program interprets binaries on its own the calculation result can be negative. UserModeLinux is such an example. It installs and removes lots of PROT_EXEC mappings but mm->start_code and mm->start_code remain and VmLib turns negative. Fix this by detecting the overflow and just return 0. For interpreting the value reported by VmLib is anyway useless but returning 0 does at least not confuse userspace. Signed-off-by: Richard Weinberger <[email protected]> --- fs/proc/task_mmu.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 8f96a49178d0..220091c29aa6 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -46,6 +46,8 @@ void task_mem(struct seq_file *m, struct mm_struct *mm) text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10; lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text; + if ((long)lib < 0) + lib = 0; swap = get_mm_counter(mm, MM_SWAPENTS); ptes = PTRS_PER_PTE * sizeof(pte_t) * atomic_long_read(&mm->nr_ptes); pmds = PTRS_PER_PMD * sizeof(pmd_t) * mm_nr_pmds(mm); -- 2.10.2
