From e47690d756a760579141560ded06ec1020dd85e8 Mon Sep 17 00:00:00 2001 From: Steven Price Date: Mon, 3 Feb 2020 17:36:42 -0800 Subject: x86: mm: avoid allocating struct mm_struct on the stack struct mm_struct is quite large (~1664 bytes) and so allocating on the stack may cause problems as the kernel stack size is small. Since ptdump_walk_pgd_level_core() was only allocating the structure so that it could modify the pgd argument we can instead introduce a pgd override in struct mm_walk and pass this down the call stack to where it is needed. Since the correct mm_struct is now being passed down, it is now also unnecessary to take the mmap_sem semaphore because ptdump_walk_pgd() will now take the semaphore on the real mm. [steven.price@arm.com: restore missed arm64 changes] Link: http://lkml.kernel.org/r/20200108145710.34314-1-steven.price@arm.com Link: http://lkml.kernel.org/r/20200108145710.34314-1-steven.price@arm.com Signed-off-by: Steven Price Reported-by: Stephen Rothwell Cc: Catalin Marinas Cc: Albert Ou Cc: Alexandre Ghiti Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Borislav Petkov Cc: Christian Borntraeger Cc: Dave Hansen Cc: David S. Miller Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: James Hogan Cc: James Morse Cc: Jerome Glisse Cc: "Liang, Kan" Cc: Mark Rutland Cc: Michael Ellerman Cc: Paul Burton Cc: Paul Mackerras Cc: Paul Walmsley Cc: Peter Zijlstra Cc: Ralf Baechle Cc: Russell King Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Will Deacon Cc: Zong Li Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/arm64/mm/dump.c | 4 ++-- arch/x86/mm/debug_pagetables.c | 10 ++-------- arch/x86/mm/dump_pagetables.c | 18 +++++++----------- 3 files changed, 11 insertions(+), 21 deletions(-) (limited to 'arch') diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c index ef4b3ca1e058..860c00ec8bd3 100644 --- a/arch/arm64/mm/dump.c +++ b/arch/arm64/mm/dump.c @@ -323,7 +323,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info) } }; - ptdump_walk_pgd(&st.ptdump, info->mm); + ptdump_walk_pgd(&st.ptdump, info->mm, NULL); } static void ptdump_initialize(void) @@ -361,7 +361,7 @@ void ptdump_check_wx(void) } }; - ptdump_walk_pgd(&st.ptdump, &init_mm); + ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); if (st.wx_pages || st.uxn_pages) pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n", diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c index d0efec713c6c..4a3b62f780b4 100644 --- a/arch/x86/mm/debug_pagetables.c +++ b/arch/x86/mm/debug_pagetables.c @@ -15,11 +15,8 @@ DEFINE_SHOW_ATTRIBUTE(ptdump); static int ptdump_curknl_show(struct seq_file *m, void *v) { - if (current->mm->pgd) { - down_read(¤t->mm->mmap_sem); + if (current->mm->pgd) ptdump_walk_pgd_level_debugfs(m, current->mm, false); - up_read(¤t->mm->mmap_sem); - } return 0; } @@ -28,11 +25,8 @@ DEFINE_SHOW_ATTRIBUTE(ptdump_curknl); #ifdef CONFIG_PAGE_TABLE_ISOLATION static int ptdump_curusr_show(struct seq_file *m, void *v) { - if (current->mm->pgd) { - down_read(¤t->mm->mmap_sem); + if (current->mm->pgd) ptdump_walk_pgd_level_debugfs(m, current->mm, true); - up_read(¤t->mm->mmap_sem); - } return 0; } diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index 411f6a758998..64229dad7eab 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -357,7 +357,8 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, } } -static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, +static void ptdump_walk_pgd_level_core(struct seq_file *m, + struct mm_struct *mm, pgd_t *pgd, bool checkwx, bool dmesg) { const struct ptdump_range ptdump_ranges[] = { @@ -386,12 +387,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, .seq = m }; - struct mm_struct fake_mm = { - .pgd = pgd - }; - init_rwsem(&fake_mm.mmap_sem); - - ptdump_walk_pgd(&st.ptdump, &fake_mm); + ptdump_walk_pgd(&st.ptdump, mm, pgd); if (!checkwx) return; @@ -404,7 +400,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm) { - ptdump_walk_pgd_level_core(m, mm->pgd, false, true); + ptdump_walk_pgd_level_core(m, mm, mm->pgd, false, true); } void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm, @@ -415,7 +411,7 @@ void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm, if (user && boot_cpu_has(X86_FEATURE_PTI)) pgd = kernel_to_user_pgdp(pgd); #endif - ptdump_walk_pgd_level_core(m, pgd, false, false); + ptdump_walk_pgd_level_core(m, mm, pgd, false, false); } EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs); @@ -430,13 +426,13 @@ void ptdump_walk_user_pgd_level_checkwx(void) pr_info("x86/mm: Checking user space page tables\n"); pgd = kernel_to_user_pgdp(pgd); - ptdump_walk_pgd_level_core(NULL, pgd, true, false); + ptdump_walk_pgd_level_core(NULL, &init_mm, pgd, true, false); #endif } void ptdump_walk_pgd_level_checkwx(void) { - ptdump_walk_pgd_level_core(NULL, INIT_PGD, true, false); + ptdump_walk_pgd_level_core(NULL, &init_mm, INIT_PGD, true, false); } static int __init pt_dump_init(void) -- cgit v1.2.3