From: Jeremy Fitzhardinge inflate_fixed and huft_build together use around 2.7k of stack. When using 4k stacks, I saw stack overflows from interrupts arriving while unpacking the root initrd: do_IRQ: stack overflow: 384 [] show_trace_log_lvl+0x1a/0x30 [] show_trace+0x12/0x14 [] dump_stack+0x16/0x18 [] do_IRQ+0x6d/0xd9 [] xen_evtchn_do_upcall+0x6e/0xa2 [] xen_hypervisor_callback+0x25/0x2c [] xen_restore_fl+0x27/0x29 [] _spin_unlock_irqrestore+0x4a/0x50 [] change_page_attr+0x577/0x584 [] kernel_map_pages+0x8d/0xb4 [] cache_alloc_refill+0x53f/0x632 [] __kmalloc+0xc1/0x10d [] malloc+0x10/0x12 [] huft_build+0x2a7/0x5fa [] inflate_fixed+0x91/0x136 [] unpack_to_rootfs+0x5f2/0x8c1 [] populate_rootfs+0x1e/0xe4 (This was under Xen, but there's no reason it couldn't happen on bare hardware.) This patch mallocs the local variables, thereby reducing the stack usage to sane levels. Also, up the heap size for the kernel decompressor to deal with the extra allocation. Signed-off-by: Jeremy Fitzhardinge Cc: Tim Yamin Cc: Andi Kleen Cc: Matt Mackall Cc: Ivan Kokshaysky Cc: Richard Henderson Cc: Russell King Cc: Ian Molton Signed-off-by: Andrew Morton --- arch/alpha/boot/misc.c | 2 arch/arm/boot/compressed/misc.c | 2 arch/arm26/boot/compressed/misc.c | 2 arch/i386/boot/compressed/misc.c | 2 arch/x86_64/boot/compressed/misc.c | 2 lib/inflate.c | 66 ++++++++++++++++++++------- 6 files changed, 54 insertions(+), 22 deletions(-) diff -puN arch/i386/boot/compressed/misc.c~deflate-stack-usage-in-lib-inflatec arch/i386/boot/compressed/misc.c --- a/arch/i386/boot/compressed/misc.c~deflate-stack-usage-in-lib-inflatec +++ a/arch/i386/boot/compressed/misc.c @@ -189,7 +189,7 @@ static void putstr(const char *); static unsigned long free_mem_ptr; static unsigned long free_mem_end_ptr; -#define HEAP_SIZE 0x3000 +#define HEAP_SIZE 0x4000 static char *vidmem = (char *)0xb8000; static int vidport; diff -puN lib/inflate.c~deflate-stack-usage-in-lib-inflatec lib/inflate.c --- a/lib/inflate.c~deflate-stack-usage-in-lib-inflatec +++ a/lib/inflate.c @@ -292,7 +292,6 @@ STATIC int INIT huft_build( oversubscribed set of lengths), and three if not enough memory. */ { unsigned a; /* counter for codes of length k */ - unsigned c[BMAX+1]; /* bit length count table */ unsigned f; /* i repeats in table every f entries */ int g; /* maximum code length */ int h; /* table level */ @@ -303,18 +302,33 @@ STATIC int INIT huft_build( register unsigned *p; /* pointer into c[], b[], or v[] */ register struct huft *q; /* points to current table */ struct huft r; /* table entry for structure assignment */ - struct huft *u[BMAX]; /* table stack */ - unsigned v[N_MAX]; /* values in order of bit length */ register int w; /* bits before this table == (l * h) */ - unsigned x[BMAX+1]; /* bit offsets, then code stack */ unsigned *xp; /* pointer into x */ int y; /* number of dummy codes added */ unsigned z; /* number of entries in current table */ + struct { + unsigned c[BMAX+1]; /* bit length count table */ + struct huft *u[BMAX]; /* table stack */ + unsigned v[N_MAX]; /* values in order of bit length */ + unsigned x[BMAX+1]; /* bit offsets, then code stack */ + } *stk; + unsigned *c, *v, *x; + struct huft **u; + int ret; DEBG("huft1 "); + stk = malloc(sizeof(*stk)); + if (stk == NULL) + return 3; /* out of memory */ + + c = stk->c; + v = stk->v; + x = stk->x; + u = stk->u; + /* Generate counts for each bit length */ - memzero(c, sizeof(c)); + memzero(stk->c, sizeof(stk->c)); p = b; i = n; do { Tracecv(*p, (stderr, (n-i >= ' ' && n-i <= '~' ? "%c %d\n" : "0x%x %d\n"), @@ -326,7 +340,8 @@ DEBG("huft1 "); { *t = (struct huft *)NULL; *m = 0; - return 2; + ret = 2; + goto out; } DEBG("huft2 "); @@ -351,10 +366,14 @@ DEBG("huft3 "); /* Adjust last length count to fill out codes, if needed */ for (y = 1 << j; j < i; j++, y <<= 1) - if ((y -= c[j]) < 0) - return 2; /* bad input: more codes than bits */ - if ((y -= c[i]) < 0) - return 2; + if ((y -= c[j]) < 0) { + ret = 2; /* bad input: more codes than bits */ + goto out; + } + if ((y -= c[i]) < 0) { + ret = 2; + goto out; + } c[i] += y; DEBG("huft4 "); @@ -428,7 +447,8 @@ DEBG1("3 "); { if (h) huft_free(u[0]); - return 3; /* not enough memory */ + ret = 3; /* not enough memory */ + goto out; } DEBG1("4 "); hufts += z + 1; /* track memory usage */ @@ -492,7 +512,11 @@ DEBG("h6f "); DEBG("huft7 "); /* Return true (1) if we were given an incomplete table */ - return y != 0 && g != 1; + ret = y != 0 && g != 1; + + out: + free(stk); + return ret; } @@ -705,10 +729,14 @@ STATIC int noinline INIT inflate_fixed(v struct huft *td; /* distance code table */ int bl; /* lookup bits for tl */ int bd; /* lookup bits for td */ - unsigned l[288]; /* length list for huft_build */ + unsigned *l; /* length list for huft_build */ DEBG(" 1) { huft_free(tl); + free(l); DEBG(">"); return i; @@ -737,11 +767,13 @@ DEBG("