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proc-vmcore: wrong data type casting fix

PATCH In review [email protected] 2 participants 3 messages Mar 11, 2016

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[email protected]

author
#0 lore raw

PATCH 2/2 proc-vmcore: wrong data type casting fix

On i686 PAE enabled machine the contiguous physical area could be large and it can cause triming down variables in below calculation in read_vmcore() and mmap_vmcore():

	tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);

Then the real size passed down is not correct any more. Suppose m->offset + m->size - *fpos being truncated to 0, buflen >0 then we will get tsz = 0. It is of course not an expected result.

During out test there are two problems caused by it:
1) read_vmcore will refuse to continue so makedumpfile fails.
2) mmap_vmcore will trigger BUG_ON() in remap_pfn_range().

Use min_lt instead so that the variables are not truncated.

Signed-off-by Baoquan He <[email protected]>
Signed-off-by Dave Young <[email protected]>
---
 fs/proc/vmcore.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
fs/proc/vmcore.c +3 -2
@@ -231,7 +231,8 @@ static ssize_t __read_vmcore(char *buffe
 
 	list_for_each_entry(m, &vmcore_list, list) {
 		if (*fpos < m->offset + m->size) {
-			tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
+			tsz = (size_t)min_lt(m->offset + m->size - *fpos,
+					    buflen);
 			start = m->paddr + *fpos - m->offset;
 			tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
 			if (tmp < 0)

@@ -461,7 +462,7 @@ static int mmap_vmcore(struct file *file
 		if (start < m->offset + m->size) {
 			u64 paddr = 0;
 
-			tsz = min_t(size_t, m->offset + m->size - start, size);
+			tsz = (size_t)min_lt(m->offset + m->size - start, size);
 			paddr = m->paddr + start - m->offset;
 			if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
 						    paddr >> PAGE_SHIFT, tsz,
#1 lore raw
Quoted 11 lines · On 03/11/16 at 02:21pm, [email protected] wrote:
fs/proc/vmcore.c +2 -1
@@ -231,7 +231,8 @@ static ssize_t __read_vmcore(char *buffe
 
 	list_for_each_entry(m, &vmcore_list, list) {
 		if (*fpos < m->offset + m->size) {
-			tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
+			tsz = (size_t)min_lt(m->offset + m->size - *fpos,
+					    buflen);
 			start = m->paddr + *fpos - m->offset;
 			tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
 			if (tmp < 0)

fs/proc/vmcore.c static int mmap_vmcore(struct file *file · line 468

Quoted 8 lines
fs/proc/vmcore.c +1 -1
@@ -461,7 +462,7 @@ static int mmap_vmcore(struct file *file
 		if (start < m->offset + m->size) {
 			u64 paddr = 0;
 
-			tsz = min_t(size_t, m->offset + m->size - start, size);
+			tsz = (size_t)min_lt(m->offset + m->size - start, size);
 			paddr = m->paddr + start - m->offset;
 			if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
 						    paddr >> PAGE_SHIFT, tsz,

Hi, Dave.

Seems the previous parameter is unsigned long long, and the later one is size_t. The size of both these types doesn't change in running time, why not use min_t(unsigned long long, a, b) instead?

Thanks
Minfei

author
#2 lore raw

Hi, Minfei

Quoted 23 lines · Minfei Huang
Quoted 11 lines · On 03/11/16 at 02:21pm, [email protected] wrote:
fs/proc/vmcore.c +2 -1
@@ -231,7 +231,8 @@ static ssize_t __read_vmcore(char *buffe
 
 	list_for_each_entry(m, &vmcore_list, list) {
 		if (*fpos < m->offset + m->size) {
-			tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
+			tsz = (size_t)min_lt(m->offset + m->size - *fpos,
+					    buflen);
 			start = m->paddr + *fpos - m->offset;
 			tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
 			if (tmp < 0)

fs/proc/vmcore.c static int mmap_vmcore(struct file *file · line 468

Quoted 8 lines
fs/proc/vmcore.c +1 -1
@@ -461,7 +462,7 @@ static int mmap_vmcore(struct file *file
 		if (start < m->offset + m->size) {
 			u64 paddr = 0;
 
-			tsz = min_t(size_t, m->offset + m->size - start, size);
+			tsz = (size_t)min_lt(m->offset + m->size - start, size);
 			paddr = m->paddr + start - m->offset;
 			if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
 						    paddr >> PAGE_SHIFT, tsz,

Hi, Dave.

Quoted 3 lines

Seems the previous parameter is unsigned long long, and the later one is size_t. The size of both these types doesn't change in running time, why not use min_t(unsigned long long, a, b) instead?

Just want a common macro so it can benefit other users so that we can simply use it without knowning type details and avoid such similar bugs also.

Thanks
Dave