Home Home > GIT Browse
summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorAndreas Schwab <schwab@linux-m68k.org>2013-08-09 15:14:08 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-20 08:21:01 -0700
commitc4e462a085dd8279af22493ad0858d73e0bcafe1 (patch)
tree7734cc9023ef437810414831414f33f92a17e23e
parent2a9a85d5fb90db72d8e0618a0fafa2069be86198 (diff)
m68k: Truncate base in do_div()
commit ea077b1b96e073eac5c3c5590529e964767fc5f7 upstream. Explicitly truncate the second operand of do_div() to 32 bits to guard against bogus code calling it with a 64-bit divisor. [Thorsten] After upgrading from 3.2 to 3.10, mounting a btrfs volume fails with: btrfs: setting nodatacow, compression disabled btrfs: enabling auto recovery btrfs: disk space caching is enabled *** ZERO DIVIDE *** FORMAT=2 Current process id is 722 BAD KERNEL TRAP: 00000000 Modules linked in: evdev mac_hid ext4 crc16 jbd2 mbcache btrfs xor lzo_compress zlib_deflate raid6_pq crc32c libcrc32c PC: [<319535b2>] __btrfs_map_block+0x11c/0x119a [btrfs] SR: 2000 SP: 30c1fab4 a2: 30f0faf0 d0: 00000000 d1: 00001000 d2: 00000000 d3: 00000000 d4: 00010000 d5: 00000000 a0: 3085c72c a1: 3085c72c Process mount (pid: 722, task=30f0faf0) Frame format=2 instr addr=319535ae Stack from 30c1faec: 00000000 00000020 00000000 00001000 00000000 01401000 30253928 300ffc00 00a843ac 3026f640 00000000 00010000 0009e250 00d106c0 00011220 00000000 00001000 301c6830 0009e32a 000000ff 00000009 3085c72c 00000000 00000000 30c1fd14 00000000 00000020 00000000 30c1fd14 0009e26c 00000020 00000003 00000000 0009dd8a 300b0b6c 30253928 00a843ac 00001000 00000000 00000000 0000a008 3194e76a 30253928 00a843ac 00001000 00000000 00000000 00000002 Call Trace: [<00001000>] kernel_pg_dir+0x0/0x1000 [...] Code: 222e ff74 2a2e ff5c 2c2e ff60 4c45 1402 <2d40> ff64 2d41 ff68 2205 4c2e 1800 ff68 4c04 0800 2041 d1c0 2206 4c2e 1400 ff68 [Geert] As diagnosed by Andreas, fs/btrfs/volumes.c:__btrfs_map_block() calls do_div(stripe_nr, stripe_len); with stripe_len u64, while do_div() assumes the divisor is a 32-bit number. Due to the lack of truncation in the m68k-specific implementation of do_div(), the division is performed using the upper 32-bit word of stripe_len, which is zero. This was introduced by commit 53b381b3abeb86f12787a6c40fee9b2f71edc23b ("Btrfs: RAID5 and RAID6"), which changed the divisor from map->stripe_len (struct map_lookup.stripe_len is int) to a 64-bit temporary. Reported-by: Thorsten Glaser <tg@debian.org> Signed-off-by: Andreas Schwab <schwab@linux-m68k.org> Tested-by: Thorsten Glaser <tg@debian.org> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/m68k/include/asm/div64.h9
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/m68k/include/asm/div64.h b/arch/m68k/include/asm/div64.h
index edb66148a71d..755803299a0f 100644
--- a/arch/m68k/include/asm/div64.h
+++ b/arch/m68k/include/asm/div64.h
@@ -13,16 +13,17 @@
unsigned long long n64; \
} __n; \
unsigned long __rem, __upper; \
+ unsigned long __base = (base); \
\
__n.n64 = (n); \
if ((__upper = __n.n32[0])) { \
asm ("divul.l %2,%1:%0" \
- : "=d" (__n.n32[0]), "=d" (__upper) \
- : "d" (base), "0" (__n.n32[0])); \
+ : "=d" (__n.n32[0]), "=d" (__upper) \
+ : "d" (__base), "0" (__n.n32[0])); \
} \
asm ("divu.l %2,%1:%0" \
- : "=d" (__n.n32[1]), "=d" (__rem) \
- : "d" (base), "1" (__upper), "0" (__n.n32[1])); \
+ : "=d" (__n.n32[1]), "=d" (__rem) \
+ : "d" (__base), "1" (__upper), "0" (__n.n32[1])); \
(n) = __n.n64; \
__rem; \
})