From: Lukas Czerner Date: Mon, 15 Oct 2012 16:56:49 +0000 (-0400) Subject: ext4: fix undefined bit shift result in ext4_fill_flex_info X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=76495ec1d47e1c0fe0673faf9179bda6bc8ab5c2;p=openwrt%2Fstaging%2Fblogic.git ext4: fix undefined bit shift result in ext4_fill_flex_info The result of the bit shift expression in '1 << sbi->s_log_groups_per_flex' can be undefined in the case that s_log_groups_per_flex is 31 because the result of the shift is bigger than INT_MAX. In reality this probably should not cause much problems since we'll end up with INT_MIN which will then be converted into 'unsigned int' type, but nevertheless according to the ISO C99 the result is actually undefined. Fix this by changing the left operand to 'unsigned int' type. Note that the commit d50f2ab6f050311dbf7b8f5501b25f0bf64a439b already tried to fix the undefined behaviour, but this was missed. Thanks to Laszlo Ersek for pointing this out and suggesting the fix. Signed-off-by: Lukas Czerner Signed-off-by: "Theodore Ts'o" Reviewed-by: Carlos Maiolino Reported-by: Laszlo Ersek --- diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 5ededf135335..8ab650b1aa1e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1970,7 +1970,7 @@ static int ext4_fill_flex_info(struct super_block *sb) sbi->s_log_groups_per_flex = 0; return 1; } - groups_per_flex = 1 << sbi->s_log_groups_per_flex; + groups_per_flex = 1U << sbi->s_log_groups_per_flex; err = ext4_alloc_flex_bg_array(sb, sbi->s_groups_count); if (err)